Showing papers in "Semiconductor Science and Technology in 1997"
TL;DR: In this article, the structural and electronic properties of lattice-mismatched Si/SiGe heterostructures are discussed in terms of scattering mechanisms and experimental results, and an assessment of the possible role of such heterodevices in future microelectronic circuits is given.
Abstract: Silicon-based heterostructures have come a long way from the discovery of strain as a new and essential parameter for band structure engineering to the present state of electron and hole mobilities, which surpass those achieved in the traditional material combination by more than an order of magnitude and are rapidly approaching the best III - V heteromaterials. It is the purpose of this article to report on the most recent developments, and the performance level achieved to date in this material system, in a concise and critical manner. The first part of this review is concerned with the structural and electronic properties of the lattice-mismatched Si/SiGe heterostructure. Emphases are put on the effects of strain both on the band structure and on the band offsets, as well as on means to actually control the strain in a stack of heteroepitaxial layers. The second part is dedicated to the transport properties of low-dimensional carrier systems in Si/SiGe and Ge/SiGe heterostructures. The prospects and limitations of the different layer concepts are discussed in terms of scattering mechanisms and experimental results. This part also reviews the most recent magneto-transport experiments on quantum wires and quantum point contacts, which became possible by the enhanced mean free paths in these materials. The third part covers the device aspects of these high-mobility materials, which is of special interest, because silicon-based heterostructures can significantly enhance the performance level of contemporary Si devices without sacrificing the essential compatibility with standard Si technologies. The recent achievements in this application-driven research field, but also the foreseeable problems and limitations, are discussed, and an assessment of the possible role of such heterodevices in future microelectronic circuits is given.
752 citations
TL;DR: In this article, the authors present a theoretical model for calculating the band structures of strained quantum-well wurtzite semiconductors, including the strain effects on the shifts of the band edges.
Abstract: We present a theoretical model for calculating the band structures of strained quantum-well wurtzite semiconductors. The theory is based on the Hamiltonian for wurtzite semiconductors and includes the strain effects on the shifts of the band edges. We show new results that include the matrix elements of the Hamiltonian using the finite-difference method for the calculations of the valence electronic band structures of quantum-well wurtzite semiconductors based on the effective-mass theory.
280 citations
TL;DR: The state of the art in understanding of electromigration induced failure is outlined in the following review as mentioned in this paper, followed by an explanation of what the consequences of electron flow directed mass transport are in circuit wiring with an emphasis on the recent appreciation of the role of mechanical stress.
Abstract: The state of the art in understanding of electromigration induced failure is outlined in the following review. An overview of the basic principles responsible for electromigration in conductors is followed by an explanation of what the consequences of electron flow directed mass transport are in circuit wiring with an emphasis on the recent appreciation of the role of mechanical stress and where it comes from. The effects of thermal stress, microstructure and precipitation are discussed within this context. Finally, suggestions for further work are made.
106 citations
TL;DR: In this article, the authors demonstrate the deposition of ZnS thin films with a thickness of 0.04 to m at temperatures ranging from 25 to C from chemical baths comprising zinc sulphate, triethanolamine and thioacetamide at pH of about 10.
Abstract: We demonstrate the deposition of ZnS thin films with a thickness of 0.04 to m at temperatures ranging from 25 to C from chemical baths comprising zinc sulphate, triethanolamine and thioacetamide at pH of about 10. The as-deposited films do not show crystallinity, are very resistive (conductivity ) and possess no photosensitivity. Annealing of the films in air at 450 to C for 1 - 2 h leads to partial conversion of the ZnS films to ZnO films. This is accompanied by an increase in the photoconductivity by more than six orders of magnitude. The optical bandgap is >3.85 eV in the as-prepared films; after annealing in air the value drops to about 3.7 eV.
90 citations
TL;DR: In this article, the authors investigated the full potential of positive resist for high-resolution pattern definition and showed that although the point spread exposure distribution is similar to that for positive PMMA, features of the order of 10 nm are easily achieved.
Abstract: Poly(methylmethacrylate) (PMMA) which is commonly used as a positive resist can also be used in a negative manner with exposure at higher dose levels. In this paper we investigate the full potential of this resist for high-resolution pattern definition. We show that although the point spread exposure distribution is similar to that for positive PMMA, features of the order of 10 nm are easily achieved. These resist structures can be transferred into the underlying materials using plasma etch techniques to a similar degree of resolution. The density of resist features is also greater than for positive PMMA with features of nm in width being possible on a 30 nm pitch. The instability of the resist structures at extreme linewidths has been identified as a potential problem in utilizing the process.
89 citations
TL;DR: In this article, random porous silicon dielectric multilayers are proposed as interesting materials for applications as optical components, where the randomness is obtained as a variation in the layer thicknesses.
Abstract: Random porous silicon dielectric multilayers are proposed as interesting materials for applications as optical components. Distributed Bragg reflectors and interferential Fabry - Perot filters are demonstrated. The randomness is obtained as a variation in the layer thicknesses. The advantage in the use of random instead of periodic multilayers lies in the obtention of a wider stop-band in Bragg reflectors with the same difference in the refractive indexes of the layers and in a higher finesse in Fabry - Perot filters.
84 citations
TL;DR: In this paper, the anisotropy of the electron Lande factor in GaAs quantum wells was determined as a function of the well width, and no difference was found between the components of the g factor parallel and perpendicular to the growth axis for a 12 nm wide QW.
Abstract: The pulsation measurement of electron spin quantum beats by time resolved photoluminescence in a magnetic field perpendicular or at to the growth axis yields the transverse and longitudinal components of the electron Lande g factor in GaAs quantum wells (QW). The anisotropy of the g factor is thus determined as a function of the well width. No difference is found between the components of the g factor parallel and perpendicular to the growth axis for a 12 nm wide QW, whereas a clear anisotropy is measured for narrower QW.
83 citations
TL;DR: Good quality thin films of bismuth selenide of thickness up to were deposited from solutions containing Bismuth nitrate, triethanolamine and N,N-dimethylselenourea maintained at temperatures ranging from room temperature to. X-ray diffraction patterns of the samples annealed at in air match the standard pattern of hexagonal (paraguanajuatite, JCPDS 33-0214) as mentioned in this paper.
Abstract: Good quality thin films of bismuth selenide of thickness up to were deposited from solutions containing bismuth nitrate, triethanolamine and N,N-dimethylselenourea maintained at temperatures ranging from room temperature to . X-ray diffraction patterns of the samples annealed at in air match the standard pattern of hexagonal (paraguanajuatite, JCPDS 33-0214). The films exhibit strong optical absorption corresponding to a bandgap of about 1.7 - 1.41 eV in the as-prepared films. These values decrease to about 1.57 - 1.06 eV upon annealing the films at for 1 h in nitrogen. As-deposited, the films show high sheet resistance in the dark. Annealing the films in air or in nitrogen enhances the dark current by about seven orders of magnitude; the resulting dark conductivity is about . This enhancement in conductivity results from improved crystallinity as well as from partial loss of selenium.
77 citations
TL;DR: Based on the physics of scattering mechanisms of MOSFET inversion layer carriers at different temperatures and vertical electric fields, a new unified mobility model of wide temperature (77 - 400 K) and range is proposed for IC simulation as mentioned in this paper.
Abstract: Based on the physics of scattering mechanisms of MOSFET inversion layer carriers at different temperatures and vertical electric fields, a new unified mobility model of wide temperature (77 - 400 K) and range is proposed for IC simulation. Measurement data taken in a wide range of temperatures and electric fields are compared with the simulation results of a MOSFET current model implementing this new mobility equation. Excellent agreement between the simulation and measurement data is found.
67 citations
TL;DR: In this paper, the authors present the temperature modelling in BSIM3v3 (Berkeley Short-Channel IGFET Model version 3), and comparison with measured data for both n- and p-channel devices with a channel length down to a quarter of a micrometre from room temperature up to C.
Abstract: This paper presents the temperature modelling in BSIM3v3 (Berkeley Short-channel IGFET Model version 3), and comparison with measured data for both n- and p-channel devices with a channel length down to a quarter of a micrometre from room temperature up to C. I - V, and are modelled with the temperature dependences of mobility, threshold voltage, saturation velocity and series resistance.
65 citations
TL;DR: In this paper, the InGaAs/AlGaAs multiple quantum well (MQW) structures with narrow (down to 26 A) well widths and large (up to 454 eV) conduction subband spacings were measured for the first time using short mid-infrared pulses from an optical parametric generator.
Abstract: Intersubband relaxation times, , in strained-layer InGaAs/AlGaAs multiple quantum well (MQW) structures with narrow (down to 26 A) well widths and large (up to 454 eV) conduction subband spacings have been measured for the first time using short mid-infrared pulses from an optical parametric generator. Absorption saturation measurements over a large dynamic range of resonant light () yield in the range 0.4 - 0.6 ps. We compare these lifetimes with those obtained for GaAs/AlGaAs structures with QW bound-to-quasibound transitions and similar subband separation. A comparison with the `standard' GaAs/AlGaAs MQW structures with bound-to-bound transitions is also made.
TL;DR: In this paper, the effect of wet chemical etching in acid solutions on the energy spectrum of n- and p-type silicon crystals previously irradiated with high-energy electrons is studied by deep-level transient spectroscopy.
Abstract: The effect of wet chemical etching in acid solutions on the energy spectrum of n- and p-type silicon crystals previously irradiated with high-energy electrons is studied by deep-level transient spectroscopy. It is observed that together with the well known radiation defects a number of novel deep-level centres appear near the etched surface. The depth profiles of the deep-level centres are investigated depending on the irradiation dose and the temperature of subsequent annealing. The novel centres observed are shown to be complexes of radiation defects with the hydrogen atoms which penetrated into the crystal during etching. The origin of some of these centres from the particular vacancy-related defects is established. A simple quantitative description is given of hydrogen atom penetration during the etching and formation of the hydrogen - radiation defect complexes. Based on this analysis, the radius of hydrogen capture to the well known A-centre (vacancy - oxygen complex) is estimated and the centre with an energy level of eV is identified as a complex of the A-centre with two hydrogen atoms.
TL;DR: In this paper, the optical transitions in undoped, hexagonal GaN layers, grown on Si(111) by molecular beam epitaxy under nitrogen-rich conditions, have been studied by photoluminescence spectroscopy.
Abstract: The optical transitions in undoped, hexagonal GaN layers, grown on Si(111) by molecular beam epitaxy under nitrogen-rich conditions, have been studied by photoluminescence spectroscopy. Several intense excitonic emissions, of free and bound character, are detected as narrow as 1.7 meV at low temperature. The free A, B and C excitons, observed at 3.4786 eV, 3.484 eV and 3.503 eV, respectively, allow the determination of the crystal-field ( meV) and spin - orbit ( meV) splittings. The evolution of their energies with temperature has been analysed with two different fits, the gap shift proportional to ) and respectively. Information on the scattering processes is obtained from the peak broadening, which is due to exciton - phonon interactions. Both the free exciton energies and their temperature behaviour agree with those observed in bulk and homoepitaxial GaN, and therefore the studied GaN/Si layers are strain-free. Up to four extrinsic transitions at 3.4755 eV, 3.4714 eV, 3.456 eV and 3.450 eV have also been observed, and their assignment to bound excitons and donor to band transitions is discussed. Finally, a band at 3.41 - 3.42 eV is attributed to a donor-to-acceptor transition. This interpretation implies the presence of an acceptor lying at 70 meV above the valence band, shallower than those usually employed for p-type doping.
Abstract: We have modelled carrier transport and impact ionization in bulk GaAs and GaAs diodes using two Monte Carlo models, one using analytical band structure, the other employing more realistic pseudopotential band structure. Despite the relative lack of sophistication of the analytical model and the poor representation of band structure at higher energies, the analytical model reproduced accurate drift velocities, mean energies and impact ionization rates in good agreement with experiment and the more sophisticated model. Both models accurately simulated the diodes, agreeing well with experimental results and the two models also agreed with each other with respect to the microscopic aspects of the carrier transport in these devices.
TL;DR: In this paper, a self-consistent analysis of the subband structure of Si-doped GaAs was performed in two different cases: (i) in the presence of a uniform electric field and inside an infinite potential barrier and (ii) under a linearly varying built-in electric field.
Abstract: We present a theoretical study of the subband structure of both single and periodically -doped GaAs layers. We will discuss the influence of the -doping concentration and the -layer spacing on the confinement properties of such structures. A self-consistent analysis is made on these -doping systems in two different cases: (i) in the presence of a uniform electric field and inside an infinite potential barrier and (ii) under a linearly varying built-in electric field and within a finite potential barrier. Two features have been observed for the Stark effect in the first case: (i) when the electric field increases, the energies of the electronic subbands become lower and simultaneously a second quantum well appears and (ii) for larger electric fields, the subband structure is dramatically changed and the main role of confining charge carriers is reversed to the new quantum well. In the second case, the Stark effect is studied by taking, as a finite barrier, the Schottky potential of a -GaAs diode. One main effect was observed: the distortion of the V-shaped potential being more or less accentuated, depending on the applied bias voltage being reverse or direct respectively. Photocurrent (PC) data of a Si -doped GaAs structure have been taken as experimental support to validate our computation.
TL;DR: In this paper, the effects of radiation damage in two silicon p - i - n photodiodes fabricated from high resistivity material have been studied, and it is suggested that irradiated silicon is relaxation material.
Abstract: The effects of radiation damage in two silicon p - i - n photodiodes fabricated from high resistivity material have been studied. The devices have been irradiated by 1 MeV neutrons to three different fluences up to . Current, capacitance and charge measurements were performed prior to irradiation and soon after. Our results indicate that the damage has degraded the charge-collection efficiency, that the devices have undergone type inversion from n-type to apparent p-type at fluences as low as , and that the substrate material has become somewhat `relaxation-like' after irradiation. It is suggested here that irradiated silicon is relaxation material.
TL;DR: In this paper, a new Raman scattering peak at, located between the bulk TO and LO frequencies, has been observed in porous layers and attributed to a surface-related phonon, which is either the depletion of the GaAs skeleton due to the surface space charge effect or the decoupling of the LO-phonon and the plasmon modes at the relative large wavevectors transferred in nanostructures.
Abstract: Porous GaAs layers have been produced by anodic etching of (100)-oriented crystalline substrates in a solution. Scanning electron microscope images showed the formation of submicron pores, the average dimension of the remaining GaAs walls being of about 100 nm. Raman scattering by LO-phonon - plasmon coupled modes, inherent in as-grown crystals, was not observed in the porous layers. Proposed explanations are either the depletion of the GaAs skeleton due to the surface space-charge effect or the decoupling of the LO-phonon and the plasmon modes at the relative large wavevectors transferred in nanostructures. A new Raman scattering peak at , located between the bulk TO and LO frequencies, has been observed in porous layers and attributed to a surface-related phonon.
TL;DR: In this paper, the effect of the distribution parameters and their bias coefficients on the barrier height and the ideality factor over a temperature range of 50 - 300 K was analyzed and the role of the series resistance in adversely influencing the linearity of the log(I) -V characteristics of a Schottky diode containing barrier inhomogeneities was discussed.
Abstract: The current - voltage (I - V) characteristics of Schottky diodes containing barrier inhomogeneities have been simulated using thermionic emission - diffusion (TED) theory and assuming a Gaussian distribution of barrier heights. The system is considered to have a number of non-interacting parallel diodes with each corresponding to a different barrier height within the distribution limit. The mean and the standard deviation of the Gaussian distribution are taken either as constant or having linear bias dependences. The simulated I - V data are then analysed to study the effects of the distribution parameters and their bias coefficients on the barrier height and the ideality factor over a temperature range of 50 - 300 K. It is shown that the mere existence of a distribution causes a decrease in the zero-bias barrier height and, in turn, leads to nonlinearity in the activation energy plots. Also, the decrease is greater for high values of standard deviation. Further, the abnormal increase of ideality factor with decrease in temperature occurs due to the bias dependence of the standard deviation of the distribution. Finally, it is demonstrated that the decrease in temperature and increase in standard deviation cause similar effects and both lead to a decrease in barrier height and an increase in ideality factor. Also, the role of the series resistance in adversely influencing the linearity of the log(I) - V characteristics of a Schottky diode containing barrier inhomogeneities is discussed.
TL;DR: In this article, the electronic properties of modulation-doped multiple quantum wells (MWQ) with well width in the range between 51 and 145? have been investigated by using the Shubnikov - de Haas (SdH) oscillations technique.
Abstract: The electronic properties of modulation-doped multiple quantum wells (MWQ) with well width in the range between 51 and 145 ? have been investigated by using the Shubnikov - de Haas (SdH) oscillations technique. The carrier density and the Fermi energy have been determined from the period of the SdH oscillations. The in-plane effective mass and the quantum lifetime of 2D electrons have been obtained from the temperature and magnetic field dependences of the SdH amplitude. For narrow MQW samples (, 75 and 78 ?), increases with decreasing ; for the samples with and 145 ?, is approximately equal to that of electrons in bulk GaAs. The values obtained for show no clear well-width dependence and suggest that interface roughness is the dominating scattering mechanism in MQWs.
TL;DR: Gold Schottky diodes have been fabricated, for the first time, on n-type GaN grown by molecular beam epitaxy as discussed by the authors, and they have been studied by I - V, C - V and deep-level transient spectroscopy.
Abstract: Gold Schottky diodes have been fabricated, for the first time, on n-type GaN grown by molecular beam epitaxy. These diodes have been studied by I - V, C - V and deep-level transient spectroscopy. The conduction process inside the diodes is shown to be by thermionic field emission. The barrier height of 1.1 eV compares well with Au Schottky diodes manufactured from n-GaN grown by metalorganic chemical vapour deposition. However, there is evidence to suggest that the grown-in deep levels are different for the two growth techniques.
TL;DR: In this article, the authors present a survey on the theoretical modelling of the small-signal response and noise associated with velocity fluctuations in semiconductor high-field transport, and compare the results of different approaches.
Abstract: We present a survey on the theoretical modelling of the small-signal response and noise associated with velocity fluctuations in semiconductor high-field transport. Because of the high values of the applied electric field, current - voltage characteristics and electrical noise are found to deviate strongly from Ohm's law and Nyquist's relation respectively. Accordingly, in the case of homogeneous (bulk) structures the field and frequency dependence of the differential mobility, diffusivity and electronic noise temperature are investigated within a rigorous microscopic approach which solves exactly the appropriate kinetic equations through analytical and Monte Carlo techniques. Spectral functions in the frequency domain are obtained from their correspondent response and correlation functions in the time domain. The subject is also analysed within a balance-equation approach which enables us to obtain simple analytical expressions which can provide a direct microscopic interpretation and can be applied to device modelling. For validation purposes calculations are applied to the relevant case of holes in Si and electrons in GaAs. In the latter material the presence of negative differential conductivity (Gunn effect) leads to interesting behaviour of the small-signal response and noise spectra which are also investigated for the simplest prototype of non-homogeneous structures, that is the diode. The comparison between the different approaches so developed and between calculations and experiments is found to be quite good, thus providing a quantitative microscopic interpretation of the main features associated with small-signal response and fluctuations in semiconductors under high-field conditions.
TL;DR: In this article, the influence of facet passivation on the noise behavior of InGaAsP/InP double-heterostructures used for laser diodes is investigated.
Abstract: The influence of facet passivation on the noise behaviour of InGaAsP/InP double-heterostructures used for laser diodes is investigated. The facet treatment with sodium sulphide resulted in a reduction of the low-frequency noise by about 30 dB (at 1 kHz). This noise reduction can clearly be attributed to the decrease of the surface state density by facet passivation. Moreover, our measurements indicate that the strong 1/f carrier noise in InGaAsP/InP semiconductor laser diodes is essentially caused by surface recombination.
TL;DR: In this article, the stability of the pigment in a dye-sensitized solid state photovoltaic nanoporous n-/cyanidin/p-CuI cell was investigated by varying the gaseous environment around the cell and the sources of light used.
Abstract: The factors determining the stability of the pigment in a dye-sensitized solid state photovoltaic nanoporous n-/cyanidin/p-CuI cell was investigated by varying the gaseous environment around the cell and the sources of light used. It is found that photodegradation of the pigment cyanidin is almost completely suppressed provided oxygen, moisture and UV-light are excluded.
TL;DR: In this article, a model based on a change of the stoichiometry of the surface region produced by the reactive ion etching was proposed to determine the barrier height change of contacts in which the GaAs substrate was dry etched.
Abstract: Ballistic electron emission microscopy (BEEM) has been applied to determine the barrier height change of contacts in which the GaAs substrate was dry etched by using . The distribution of barrier heights over the contact area could be determined. It was found that dry etching introduced a second Gaussian distribution, with lower mean barrier height, next to the Gaussian distribution already found to be present in wet etched reference samples. This additional distribution occurred over the main part of the contact area. A model is proposed based on a change of the stoichiometry of the surface region produced by the reactive ion etching.
TL;DR: In this article, a Monte Carlo simulation of the electron dynamics in the channel, coupled with a solution of the two-dimensional Poisson equation including inversion-layer quantization and drift-diffusion equations, has been developed.
Abstract: The dependence of the electron mobility on the longitudinal electric field in MOSFETs has been studied in detail. To do so, a Monte Carlo simulation of the electron dynamics in the channel, coupled with a solution of the two-dimensional Poisson equation including inversion-layer quantization and drift-diffusion equations, has been developed. A simplified description of the silicon band structure in the effective-mass approximation including non-parabolicity has been considered. Different-channel-length MOSFETs and different biases have been taken into account. It has been shown that in order to accurately describe electron-mobility behaviour in short-channel MOSFETs it is necessary to take into account the electron-velocity overshoot. An analytical expression, easy to include in device simulators, is provided to account for the dependence of the electron mobility on the high values of the longitudinal electric field and of its gradient found in state-of-the-art MOSFETs.
TL;DR: The p-type nature of the nickel oxide film allows holes to be injected from the valence band of the contact, and hence at a lower applied voltage than that required for indium tin oxide contacts as discussed by the authors.
Abstract: Porous silicon electroluminescent devices have been fabricated from n-type substrates using indium tin oxide, hole-transporting poly(9-vinyl carbazole) and p-type nickel oxide films as hole injecting contacts. The addition of the polymer layer, which increases the contact area by penetrating into the porous microstructure, leads to an increase in the device quantum efficiency of two orders of magnitude. The replacement of indium tin oxide by nickel oxide, formed by a thermal evaporation process, lowers the device switch-on voltage from 55 - 60 V to 10 - 15 V. The p-type nature of the nickel oxide film allows holes to be injected from the valence band of the contact, and hence at a lower applied voltage than that required for indium tin oxide contacts. The luminescence power output from both devices is similar, and we suggest that the limiting factor in the luminescent output is the rate of carrier flow throughout the device nanostructures.
ETSI1
TL;DR: In this paper, the characteristics of reactive ion etching of gallium nitride layers, using etching gas, were investigated, and the GaN etch rate was examined by varying the bias voltage and the flow rate of.
Abstract: The characteristics of reactive ion etching of gallium nitride layers, using etching gas are investigated. The GaN etch rate is examined by varying the bias voltage and the flow rate of . For bias voltages in the range of 250 V to 400 V, the etch rate is found to increase with voltage, attaining a maximum rate of at 400 V. The rate also increases with increasing flow. The addition of an inert gas, Ar, or of a reactive gas, , is found to barely affect the etch rate. Surface morphology after etching is checked by atomic force microscopy and scanning electron microscopy, which show that the smoothness of the etched surface is comparable to that of the unetched, and the etched sidewall forms an angle of to the surface normal.
TL;DR: In this article, the effects of postdeposition processes such as dip and/or annealing in air on the material and device properties of vacuum-evaporated Au-CdTe/CdS-TO heterojunction solar cells have been investigated.
Abstract: The effects of post-deposition processes such as dip and/or annealing in air on the material and device properties of vacuum-evaporated Au-CdTe/CdS-TO heterojunction solar cells have been investigated. The dip followed by air annealing at for 5 min improved the device efficiency significantly, resulting in decreased CdTe resistivity and enhanced grain size. The temperature-dependent current - voltage analysis indicated that above 280 K interface recombination dominates the current transport mechanism for the as-grown samples, while depletion region recombination starts to be dominant after annealing the samples with . Below 280 K multistep tunnelling is identified to be the dominant transport mechanism. Frequency-dependent capacitance - voltage studies revealed that after annealing with the density of interface states decreases and the quality of the heterointerface improves. The capacitance of the CdS/CdTe heterojunctions has been analysed using a model based on the existence of a single dominant trap level, identified at 0.40 eV above the valence band with a concentration of .
IBM1
TL;DR: In this article, the energy spacing of spin and valley split energy levels in strained Si quantum wells was determined using tilted-magnetic-field Shubnikov-de Haas measurements.
Abstract: The energy spacing of spin- and valley-split energy levels in strained Si quantum wells is determined using tilted-magnetic-field Shubnikov - de Haas measurements. The effective Lande g-factor, , is determined both as a function of electron sheet concentration, , and Landau level occupation number, . The value of is determined from the angle at which the longitudinal magnetoresistance minima of adjacent spin-split Landau levels are equal. For the coincidence of the and levels, increases from to as is decreased from to at T = 0.4 K. In the same sample, with fixed electron concentration of , for , and oscillates between average values of and , for lower values of . The magnitude of the valley splittings has also been investigated; for a perpendicular magnetic field of , a splitting of is determined, which is several times smaller than values for Si inversion layers reported in the literature.
TL;DR: In this article, it was shown that it is not yet possible to design, grow or qualify the semiconductor multilayers with sufficient accuracy, precision, uniformity or reproducibility that would allow reverse engineering, a prerequisite for manufacture, to be undertaken with confidence.
Abstract: In spite of many remarkable prototype device performances reported using semiconductor multilayers that incorporate thin tunnel barriers, it has never been established that the devices are capable of routine manufacture. With reference to the simplest possible tunnel device structure, a single thick AlAs barrier within an asymmetric doping environment in GaAs (the so-called ASPAT microwave detector diode), we show here that is not yet possible to design, grow or qualify the semiconductor multilayers with sufficient accuracy, precision, uniformity or reproducibility that would allow reverse engineering, a prerequisite for manufacture, to be undertaken with confidence. We describe the improvements in design, growth and qualification that will be required to achieve manufacturability, and comment on the feasibility of attaining this goal. Our conclusions for thin tunnel barrier device concepts apply a fortiori to any device ideas that seek to exploit mesoscopic phenomena in semiconductors.