Showing papers in "Semiconductor Science and Technology in 1999"
TL;DR: In this paper, a long-lifetime violet InGaN multi-quantum-well/GaN/AlGaN separate-confinement heterostructure laser diodes (LDs) were successfully fabricated using epitaxially laterally overgrown GaN by reducing a large number of threading dislocations originating from the interface between GaN and sapphire substrate.
Abstract: High-efficiency light-emitting diodes emitting amber, green, blue and ultraviolet light have been obtained through the use of InGaN active layers instead of GaN active layers. The localized energy states caused by In composition fluctuation in the InGaN active layer seem to be related to the high efficiency of the InGaN-based emitting devices. Long-lifetime violet InGaN multi-quantum-well/GaN/AlGaN separate-confinement heterostructure laser diodes (LDs) were successfully fabricated using epitaxially laterally overgrown GaN by reducing a large number of threading dislocations originating from the interface between GaN and sapphire substrate. The threading dislocations shorten the lifetime of the LDs through an increase of the threshold current density. The LDs with cleaved mirror facets showed an output power as high as 30 mW under room-temperature continuous-wave (CW) operation with a stable fundamental transverse mode. The lifetime of the LDs at a constant output power of 5 mW was estimated to be approximately 3000 h under CW operation at an ambient temperature of 50 °C. These results indicate that these LDs already can be used for many real applications, such as digital versatile disks, laser printers, sensors and exciting light sources as a commercial product with a high output power and a high reliability.
228 citations
TL;DR: Raman spectroscopy was used for analysis of phase transformations and residual stress in machined silicon wafers as discussed by the authors, where wear debris from dicing of silicon was scanned with a Raman spectrometer.
Abstract: Raman spectroscopy was used for analysis of phase transformations and residual stress in machined silicon. Wear debris from dicing of silicon was scanned with a Raman spectrometer. Recorded spectra manifest the presence of amorphous Si, hexagonal phase (Si-IV), bc8 phase (Si-III) and pristine Si-I under residual stress. On surfaces of diced wafers as well as lapped silicon wafers, the r8 phase (Si-XII) was detected in addition to the above phases. The composition of phases in diced cross sections of silicon wafers differs dramatically between high and low speed cuts. The quantification of these phases was attempted by curve fitting each spectrum with corresponding peaks of each phase. Subsequently, relative intensity maps of specific phases were generated. Thus, Raman spectroscopy studies of machined surfaces demonstrated metallization of Si under a variety of machining conditions including lapping, grinding, scratching, dicing and slicing. All metastable phases of silicon disappear after etching and polishing of respective wafers. No evidence of phase transformations was found on a quartz-damaged silicon wafer surface. Residual stress having a characteristic distribution was observed in this case.
199 citations
TL;DR: A series of calculations have been performed on group-III nitrides (GaN, AlN and InN) in both zinc-blende and wurtzite structures.
Abstract: A series of calculations have been performed on group-III nitrides (GaN, AlN and InN) in both zinc-blende and wurtzite structures. Three different levels of computation have been performed in an integrated programme of study: first-principles total energy calculations, semi-empirical pseudopotential calculations and calculations. Bandstructures are obtained from each method in a consistent manner, and used to provide effective masses and parameters for planned work on the electronic structure of alloys and quantum well heterostructures.
161 citations
TL;DR: In this paper, the photoconductivity/dark conductivity ratio (Gph/Gdark) of vacuum-evaporated tin sulfide (SnS) thin films on glass substrates with copper contacts was investigated.
Abstract: Annealing in air and argon each produces an increase of a factor of 5 or more in the photoconductivity/dark conductivity ratio (Gph/Gdark) of vacuum-evaporated tin sulfide (SnS) thin films on glass substrates with copper contacts. No significant increase in Gph/Gdark is observed after annealing SnS thin films with silver contacts. Annealing in air at or above 250 °C for 5 min dramatically increases the dark conductivity of the films. Annealing in Ar produces no significant increase in dark conductivity. It is probable that the rise in dark conductivity that accompanies annealing in air is caused by thermal activation of oxygen acceptors followed at higher temperatures by the conversion of SnS to SnO2. The films display photoconductivity from the near-infrared to the ultraviolet. The thinnest films we have produced (18 nm) display the highest Gph/Gdark and are three times more photoconductive at 400 nm than they are at 700 nm.
150 citations
TL;DR: In this article, a brief review of classification, application and sources of near-ultraviolet (UV) radiation the methods for fabricating UV photodetectors and characteristics of the photoconductive cells, p-n junction structure and Schottky barrier photodiodes are discussed.
Abstract: After a brief review of classification, application and sources of near-ultraviolet (UV) radiation the methods for fabricating UV photodetectors and characteristics of the photoconductive cells, p-n junction structure and Schottky barrier photodiodes are discussed. Characteristics of some light filters used in photodetectors and measuring devices are also reported. Now Si p-n structures are commonly used but Schottky diodes based on wide-gap (GaAsP, GaP, GaN, AlGaN, SiC) semiconductors are very attractive. They are insensitive to the infrared radiation and if necessary simple glass filters can be used for correcting the spectrum in such way that it covers just the near-UV region.
122 citations
TL;DR: In this paper, the distribution of Schottky barrier heights over the contact area in Au/III-V semiconductor (GaAs, InP, AlxGa1-xA, InxGa 1-xAs) diodes was determined using ballistic electron emission microscopy.
Abstract: The distribution of Schottky barrier heights over the contact area in Au/III-V semiconductor (GaAs, InP, AlxGa1-xAs, InxGa1-xAs) diodes was determined using ballistic electron emission microscopy. Samples which received a chemical pretreatment in aqueous HF or HCl solutions showed changes in the barrier height distribution. In some cases, short rinses in deionized water could remove these effects. Additional XPS measurements and our former work on Si enabled us to propose a model wherein negatively charged species containing F or Cl at the interface are assumed to be responsible for these changes in barrier height distribution. However, in some cases, these effects were shadowed by more drastic influences due to the chemical processing such as changes in the stoichiometry of the surface region.
115 citations
TL;DR: Gain characteristics of injection lasers based on self-organized quantum dots (QDs) were studied experimentally for two systems: InGaAs QDs in an AlGaAs matrix on a GaAs substrate as discussed by the authors.
Abstract: Gain characteristics of injection lasers based on self-organized quantum dots (QDs) were studied experimentally for two systems: InGaAs QDs in an AlGaAs matrix on a GaAs substrate and InAs QDs in an InGaAs matrix on an InP substrate. A ground-to-excited state transition was observed with increasing threshold gain. An empirical equation is proposed to fit the current density dependence of the QD gain. This fitting equation is shown to be valid for both the ground and excited state lasing in the systems under study in the 77-300 K temperature range. The effect of QD surface density on gain characteristics is calculated analytically.
80 citations
TL;DR: A review of the magnetothermoelectric properties of semiconductors can be found in this article, where the main conclusion is that the experimental observations on electrons, holes, two-carrier systems and composite fermions are consistent with physical models and predictions based on the Boltzmann equation.
Abstract: This topical review examines work on the magnetothermoelectric properties of semiconductors that has appeared since the major review by Gallagher and Butcher in 1992. The focus is on the field dependence of the thermopower of degenerate two- and three-dimensional systems, both diffusion and phonon drag. The main conclusion is that the experimental observations on electrons, holes, two-carrier systems and composite fermions are all consistent with physical models and predictions based on the Boltzmann equation. A brief review of the possible effect of weak localization on phonon drag is also given.
71 citations
TL;DR: In this article, the conduction band offset of the type II heterostructure CdS/ZnSe was determined from photoluminescence data of single quantum wells, which were grown by compound-source molecular-beam epitaxy.
Abstract: The conduction band offset of the type II heterostructure CdS/ZnSe is determined from photoluminescence data of single quantum wells. The cubic quantum well samples have been grown by compound-source molecular-beam epitaxy. Photoluminescence spectra were measured at low temperatures and evaluated by fitting an effective mass model to the transition energies. A conduction band offset of (0.80±0.1) eV and an effective electron mass for cubic CdS of (0.18±0.05)m0 were determined.
54 citations
TL;DR: In this article, the authors used TCAD to determine that the bulk low field mobility of the strained silicon which forms the channel is 1500 cm2 V-1 s-1, while the source-drain series resistance is 1.5 mm.
Abstract: Heterojunction MOSFETs (HMOSFETs), grown on a virtual substrate of SiGe and having a strained silicon channel, have been fabricated. A conventional silicon MOS process was used, including dry thermal oxidation and high temperature source-drain annealing. Good transistor I-V characteristics were obtained for devices having drawn gate lengths between 150 nm and 10 µm and an extrinsic transconductance of 220 mS mm-1 is reported for the 150 nm gate length device. Technology computer aided design (TCAD) is used to determine that the bulk low field mobility of the strained silicon which forms the channel is 1500 cm2 V-1 s-1, while the source-drain series resistance is 1.5 mm. Good agreement between simulated and experimental I-V data is obtained.
53 citations
TL;DR: In this article, a microscopic study of 0.1 µm recessed gate -doped AlInAs/GaInAs HEMTs has been performed by using a semiclassical Monte Carlo device simulation.
Abstract: A microscopic study of 0.1 µm recessed gate -doped AlInAs/GaInAs HEMTs has been performed by using a semiclassical Monte Carlo device simulation. The geometry and layer structure of the simulated HEMT is completely realistic, including recessed gate and -doping configuration. The usual T-gate technology is used to improve the device characteristics by reducing the gate resistance. For first time we take into account in the Monte Carlo simulations the effect of the T-gate and the dielectric used to passivate the device surface, which affects considerably the electric field distribution inside the device. The measured Id-Vds characteristics of a real device are favourably compared with the simulation results. When comparing the complete simulation with the case in which Poisson equation is solved only inside the semiconductor, we find that even if the static I-V characteristics remain practically unchanged, important differences appear in the dynamic and noise behaviour, reflecting the influence of an additional capacitance.
TL;DR: In this article, the vibrational mode of isolated hydrogen molecules in float zone silicon has been investigated and it has been shown that hydrogen molecules diffuse to boron acceptors and that there is subsequent dissociation of these molecules with the formation of H-B pairs.
Abstract: Boron-doped, float zone silicon has been hydrogenated at C and then quenched to room temperature. Infrared absorption measurements of the samples in their as-quenched state and following anneals at C reveal the vibrational mode from H-B pairs, together with the line that we have assigned to the vibrational mode of isolated hydrogen molecules . Annealing leads to irreversible increases in the concentrations of H-B pairs and decreases in the concentration of centres. The results imply that molecules diffuse to boron acceptors and that there is subsequent dissociation of these molecules with the formation of H-B pairs. The measurements confirm an earlier proposal that `hidden hydrogen' present in such samples is in the form of isolated molecules.
TL;DR: In this paper, the magnetic field dependence of the onset of the current steps was determined to determine the lateral extension of the electronic wave function in the dot to 4 nm, corresponding to a dot of 14 nm in diameter.
Abstract: Tunnelling experiments through GaAs-AlAs-GaAs structures with InAs embedded in the AlAs barrier show steps in the current-voltage characteristics which we assign to single-electron tunnelling through self-assembled InAs quantum dots between two three-dimensional electrodes. From the magnetic field dependence of the onset of the current steps, we determine the lateral extension of the electronic wave function in the dot to 4 nm, corresponding to a dot of 14 nm in diameter. Replica of steps at higher voltages are attributed to tunnelling through charged dots. A similar structural dot size is measured independently by transmission electron microscopy on the same wafer and by atomic force microscopy on control samples with InAs dots on a GaAs or an AlAs surface, respectively.
TL;DR: A dye-sensitized photoelectrochemical cell made from a nano-porous composite film consisting of tin(IV) and zinc oxides generates exceptionally high photocurrents at an optimum mixing ratio of the two oxides as discussed by the authors.
Abstract: A dye-sensitized photoelectrochemical cell made from a nano-porous composite film consisting of tin(IV) and zinc oxides generates exceptionally high photocurrents at an optimum mixing ratio of the two oxides. It is suggested that this phenomenon originates from ballistic transport of electrons injected by the excited dye molecules along the interconnected chains of tin(IV) oxide nanocrystallites to a zinc oxide crystallite.
TL;DR: In this paper, successive depositions increase the uniformity and homogeneity of multilayered sol-gel tin oxide films, and the final thickness is always found to be lower than a multiple of the initial first layer thickness.
Abstract: When prepared by the sol-gel dip-coating technique, doped tin oxide films need several superimposed layers to reach the expected low sheet resistance. In this paper we show that successive depositions increase the uniformity and homogeneity of multi-layered sol-gel tin oxide films. The final thickness is always found to be lower than a multiple of the initial first layer thickness, indicating that densification occurs. A strong improvement of physical properties is jointly observed in this multilayered configuration. All parameters (atomic density, refractive index, electrical resistivity, optical transmission and reflectivity) evolve towards bulk material values. This is explained by the fact that the sol, in which is dipped the substrate, fills in the pores or cracks remaining in the previously deposited layers. The quality of the sol-gel tin oxide stacked deposits obtained in such a way is evidenced by the M-line spectroscopy experiments presented in this paper. It is shown that multilayered coatings are able to guide light over some millimetres.
TL;DR: In this article, three different ways to control the electronic spectrum of InAs-based quantum dots (QDs) formed by self-organization phenomena during the initial stages of strained layer epitaxy are reviewed.
Abstract: Recent achievements in controlling the electronic spectrum of InAs-based quantum dots (QDs) formed by self-organization phenomena during the initial stages of strained layer epitaxy are reviewed. Three different ways to exercise this control are discussed, based on variation of QD size with the amount of QD material deposited, tuning of the electronic levels in QDs by changing the matrix bandgap, and electronic coupling of neighbouring QDs vertically stacked in the growth direction. Possibilities to prevent thermal evaporation of carriers out of QD states and to tune the emission wavelength in the range 0.85-1.3 µm on GaAs substrates and up to 2 µm on InP substrates are demonstrated.
TL;DR: In this article, Si-doped AlxGa1-xN (0 x 0.35) epitaxial layers grown on sapphire were used for ultraviolet photoconductive detectors.
Abstract: We report on the fabrication and characterisation of ultraviolet photoconductive detectors based on Si-doped AlxGa1-xN (0 x0.35) epitaxial layers grown on sapphire. The peak responsivity shifts from 365 nm to 300 nm for increasing Al contents. The devices present high responsivities (~100 A W-1 for Popt = 1 W m-2), which strongly depend on the incident optical power. This behaviour is explained by a light-induced modulation of the conductive area. In addition, the responsivity increases with carrier concentration and mobility, as also predicted by this model. Persistent photoconductivity decreases with doping, whatever the Al content, because of the enhancement of tunnel recombination across the potential barriers generated by surface and defects. Photocurrent decays have been successfully modelled by taking into account both the thermoionic and tunnel relaxation mechanisms, the latter being dominant even for undoped GaN.
TL;DR: The photoluminescence and photoconductivity measurements in epitaxial films are presented in this article, where the peak energy changes with temperature exhibiting an inverted S-shape dependence, where it decreases, then increases with increasing temperature in the range 40-100 K and finally decreases with an increasing temperature.
Abstract: Results of photoluminescence and photoconductivity measurements in epitaxial films are presented. The photoluminescence peak energy and intensity show several anomalous behaviours. The peak energy changes with temperature exhibiting an inverted S-shape dependence, where it decreases, then increases with increasing temperature in the range 40-100 K and finally decreases with increasing temperature. The intensity shows a temperature dependence similar to that of amorphous semiconductors and disordered superlattices. A blue shift of the photoluminescence energy with increasing excitation intensity is observed. A large Stokes shift between the photoluminescence peak position and the band edge transition energy is found; it decreases with decreasing indium content. A persistent photoconductivity effect has been detected up to room temperature with a stretched-exponential function for its decay rate. All these observations can be explained in a consistent way by alloy potential fluctuations, and these clearly indicate the existence of compositional fluctuations. These two related effects thus appear to constitute the mechanism for the widely observed localized excitons in InGaN-based devices.
TL;DR: In this paper, the epitaxial growth of high-quality ZnS films on sapphire and silicon substrates, using pulsed laser deposition, was reported for the first time, and X-ray diffraction data yield full width at half maximum 2theta values of 0.13° for as-grown samples.
Abstract: We report for the first time, epitaxial growth of high-quality ZnS films on sapphire and silicon substrates, using pulsed laser deposition. X-ray diffraction results show that at all growth temperatures from 200°C to 680°C, epitaxial wurtzite (002) ZnS films have been successfully grown on (1012) sapphire and (001) silicon substrates. X-ray diffraction data yield full width at half maximum 2theta values of 0.13° for as-grown samples, compared with 28 values or 0.09° and 0.08° for the bare sapphire and silicon substrates respectively.
TL;DR: The spin relaxation times of electrons in InGaAs(P)/InGaAsP multiple quantum wells have been directly measured as a function of well width using an ultrashort pulse color center laser as mentioned in this paper.
Abstract: The spin relaxation times of electrons in InGaAs(P)/InGaAsP multiple quantum wells have been directly measured as a function of well width using an ultrashort pulse colour centre laser. The times measured range from 20 to 5 ps, considerably faster than previously determined in GaAs quantum wells. In addition, a fast, all-optical polarization switch based on a spin-sensitive optical nonlinearity is demonstrated at a wavelength of . This operating wavelength and the observed switch recovery time of 5.5 ps make it a potentially useful element for future all-optical soliton communication systems.
TL;DR: In this article, the authors investigated the photoluminescence (PL) spectra of TlInS2 layered single crystals in the 500-860 nm wavelength region and in the 11.5-100 K temperature range.
Abstract: Photoluminescence (PL) spectra of TlInS2 layered single crystals were investigated in the 500-860 nm wavelength region and in the 11.5-100 K temperature range. We observed two PL bands centred at 515 nm (2.41 eV, A band) and 816 nm (1.52 eV, B band) at T = 11.5 K and an excitation intensity of 7.24 W cm-2. A detailed study of the A band was carried out as a function of temperature and excitation laser intensity. A red shift of the A band position was observed for both increasing temperature and decreasing excitation laser intensity in the range from 0.12 to 7.24 W cm-2. Analysis of the data indicates that the A band is due to radiative transitions from the moderately deep donor level located at 0.25 eV below the bottom of the conduction band to the shallow acceptor level located at 0.02 eV above the top of the valence band. An energy-level diagram for radiative donor-acceptor pair transitions in TlInS2 layered single crystals is proposed.
TL;DR: In this paper, a lateral effective potential is proposed to calculate the electron and hole states in V-groove quantum wires, which is used together with a suitable coordinate transformation which results in two decoupled one-dimensional Schrodinger equations.
Abstract: We propose a lateral effective potential which allows a straightforward calculation of electron and hole states in V-groove quantum wires. This effective potential is used together with a suitable coordinate transformation which results in two decoupled one-dimensional Schrodinger equations which are readily solved. The energy levels and wave functions calculated by this method are in close agreement with several previous results, which indicates that this method may be valuable for the study of physical properties in V-shaped quantum wires which require analytically calculated wave functions. Also, the proposed effective potential gives rise to a shallow vertical quantum well which is found in some V-groove quantum wire structures.
TL;DR: In this article, the stress-induced leakage current (SILC) of a 42 nm SiO2 layer is investigated during constant gate voltage stress of metal-oxide-semiconductor capacitors.
Abstract: The stress-induced leakage current (SILC) of a 42 nm SiO2 layer is investigated during constant gate voltage stress of metal-oxide-semiconductor capacitors The density of bulk electron traps generated during the electrical stress is extracted from the SILC contribution, assuming a trap-assisted tunnelling mechanism It is shown that a fixed critical value for the density of traps is reached at breakdown or soft breakdown of the SiO2 layer, independent of the gate voltage stress A physical model based on the formation of a percolation path between the bulk electron traps randomly generated during the stress is proposed to link SILC to time-dependent dielectric breakdown in ultra-thin gate oxides The validity of this model with respect to positive and negative stress polarities is discussed It is also shown that this model allows us to predict the reliability of ultra-thin gate oxide layers at low applied gate voltage stress
TL;DR: In this paper, the effect of self-adjustment of the cavity mode in vertical cavity surface-emitting lasers containing three-period InGaAs-GaAs vertically-coupled quantum dots has been observed.
Abstract: The effect of self-adjustment of the cavity mode in vertical cavity surface-emitting lasers containing three-period InGaAs-GaAs vertically-coupled quantum dots has been observed. The effect originates from a strong modulation of the refractive index near the gain peak, caused by excitons in quantum dots. The possibility of single quantum dot lasing is demonstrated.
TL;DR: In this article, the rare earth element Gd was introduced into the liquid phase during LPE growth, and it was shown that the carrier concentration of InAs layers can be effectively reduced to.
Abstract: In this paper, we report the growth of very pure InAs epitaxial layers of high quantum efficiency, by introducing the rare-earth element Gd into the liquid phase during LPE growth. We find that the carrier concentration of InAs layers can be effectively reduced to . Also, the peak photoluminescence (PL) intensity of such layers can be considerably increased by between ten- and 100-fold compared with untreated material. We attribute this behaviour to the gettering of residual impurities and corresponding reduction of non-radiative recombination centres in the presence of Gd. Four intense sharp lines dominated the low temperature (4 K) photoluminescense spectra of Gd-treated InAs layers. The strongest two of these were found to originate from (a) bound excitons, and (b) donor-acceptor recombination, whereas the remaining two, (c) and (d), were associated with defect-related recombination. The linewidth (FWHM) of the exciton peak (a) was reduced to only 3.8 meV, which is narrower than for undoped epitaxial InAs grown by MBE or MOVPE.
TL;DR: In this article, the authors calculate the effect of the native interface asymmetry on the band structure of (InGa)As-InP quantum wells and show that it leads to a new contribution to the spin-splitting in both the valence and conduction subbands.
Abstract: In this article we calculate the effect of the native interface asymmetry on the band structure of `no common atom' quantum wells such as (InGa)As-InP. We show that it leads to a new contribution to the spin-splitting in both the valence and conduction subbands. The splitting appears to be anisotropic and at least one order of magnitude larger in the valence subbands than in the conduction subbands.
TL;DR: In this paper, high-resolution photoinduced transient spectroscopy and the modulated photocurrent technique are compared in terms of possible application to the investigation of defect levels in semi-insulating monocrystalline materials.
Abstract: High-resolution photoinduced transient spectroscopy and the modulated photocurrent technique are compared in terms of possible application to the investigation of defect levels in semi-insulating monocrystalline materials. After a description of the theoretical and experimental aspects, the advantages, drawbacks and limitations of each method are discussed. The two techniques complement each other and their potentialities are exemplified by the measurements of trap parameters in the same samples of semi-insulating Cr-doped and undoped GaAs. From these results we deduce a possible model for the properties of the Cr defect in GaAs.
TL;DR: In this paper, an active layer based on multiquantum wells has been evaluated by means of a separate-confinement laser diode structure grown on a GaSb substrate by molecular beam epitaxy.
Abstract: Gallium antimonide and related compounds are promising materials for fabricating monolithic vertical cavity semiconductor lasers operating at telecommunications wavelengths. With that aim active layers based on multiquantum wells have been evaluated by means of a separate-confinement laser diode structure grown on a GaSb substrate by molecular beam epitaxy. Owing to optimization of the growing process, for the well/barrier structure, laser emission at 1.4 m has been obtained at 80 K with a threshold current as low as 15 mA for a 640 m long and 15 m wide mesa stripe structure. At room temperature laser emission occurred at 1.55 m with a pulsed threshold current density of 4 kA according to the measured characteristic temperature of 50 K. In a first attempt such an active layer has been included in a 1.5 m microcavity involving antimonide Bragg mirrors.
TL;DR: In this article, two major current mechanisms were included into balance equations for the p-n junction: trap-assisted tunnelling (TAT) and Shockley-Reed-Hall generation-recombination processes for a defect trap level in the gap.
Abstract: Dark carrier transport mechanisms in Hg1-xCdxTe (x = 0.19-0.265) photodiodes in the temperature range 70-150 K and PbTe1-ySy/Pb1-xSnxTe (x = 0.2, y = 0.03) heterojunctions at T = 80 K are discussed. Two major current mechanisms were included into balance equations for the p-n junction: trap-assisted tunnelling (TAT) and Shockley-Reed-Hall generation-recombination processes for a defect trap level in the gap. Other current mechanisms (band-to-band tunnelling, bulk diffusion, etc) were taken into account as additive contributions. For TAT Anderson's matrix element of the impurity ionization was used and the tunnelling rate characteristics were calculated in the k-p approximation with constant barrier field. Using donor and acceptor concentrations in n- and p-type regions of the diode, trap level concentration, trap level energy and the in-junction trap level lifetimes as fitting parameters, a relatively good agreement with the experimental data for HgCdTe and PbSnTe diodes with large zero-resistance-area products R0A (e.g. for the 10 µm spectral region R0A>10 cm2) was obtained, which allows one to deduce the parameters of mercury-cadmium telluride and lead-tin telluride photodiodes from the parameters of the materials used for the diode fabrication. For the diodes with poor R0A characteristics (R0A<1 cm2 for the 10 µm spectral region) the agreement with the experimental data is not so good, which is apparently caused by the presence of several types of traps with different energy positions inside the gap and with different properties.
TL;DR: In this article, the Stranski-Krastanov growth mode and migration mechanism of Ge atoms on Si substrates were investigated to obtain highly regular dot arrays with excellent size uniformity in the nanoscale.
Abstract: Selective epitaxial growth of Ge dot structures is investigated to obtain highly regular dot arrays with excellent size uniformity in the nanoscale. The dot structures are grown in patterned fine windows ranging in diameter from 650 to 90 nm on Si(100) substrates covered with masks. The dimensions and number of the dots grown in a window significantly change depending on window size, growth temperature and time and the thickness of the Si buffer layer. These growth characteristics are considered to be induced by the Stranski-Krastanov growth mode and migration mechanism of Ge atoms on Si substrates. It is noted that Ge dots whose diameter is much smaller than the pattern size are formed with high uniformity and that the position is precisely controlled by SEG. The Ge dot structures are found to give rise to prominent luminescence with well separated phonon replicas and the energy position systematically changes when the growth conditions are varied.