Showing papers on "Doping published in 1976"

Amorphous silicon solar cell

Abstract: Thin film solar cells, ∼1 μm thick, have been fabricated from amorphous silicon deposited from a glow discharge in silane. The cells were made in a p‐i‐n structure by using doping gases in the discharge. The best power conversion efficiency to date is 2.4% in AM‐1 sunlight. The maximum efficiency of thin‐film amorphous silicon solar cells is estimated to be ∼14–15%.

Measurements of bandgap narrowing in Si bipolar transistors

Abstract: Theory predicts appreciable bandgap narrowing in silicon for impurity concentrations greater than about 1017 cm−3. This effect influences strongly the electrical behaviour of silicon devices, particularly the minority carrier charge storage and the minority carrier current flow in heavily doped regions. The few experimental data known are from optical absorption measurements on uniformly doped silicon samples. New experiments in order to determine the bandgap in silicon are described here. The bipolar transistor itself is used as the vehicle for measuring the bandgap in the base. Results giving the bandgap narrowing (ΔVg0) as a function of the impurity concentration (N) in the base (in the range of 4.1015–2.5 1019 cm−3) are discussed. The experimental values of ΔVg0 as a function of N can be fitted by: δV g0 = V 1 ln N N 0 + ln 2 N N 0 +C where V1, N0 and C are constants. It is also shown how the effective intrinsic carrier concentration (nie) is related with the bandgap narrowing (ΔVg0).

Electronic properties of substitutionally doped amorphous Si and Ge

Abstract: It is shown that substitutional doping of an amorphous semiconductor is possible and can provide control of the electronic properties over a wide range. a-Si and Ge specimens have been prepared by the decomposition of silane (or germane) in a radio-frequency (r.f.) glow discharge. Doping is achieved by adding carefully measured amounts of phosphine or diborane, between 5 × 10−6 and 10−2 parts per volume, to obtain n- or p-type specimens. The room temperature conductivity of doped a-Si specimens can be controlled reproducibly over about 10 orders of magnitude, which corresponds to a movement of the Fermi level of 1·2 eV. Ion probe analysis on phosphorus doped specimens indicates that about half the phosphine molecules in the gaseous mixture introduce a phosphorus atom into the Si random network; it is estimated that 30–40% of these will act as substitutional donors. The results also show that the number of incorporated phosphorus atoms saturates at about 3 × 1019 cm−3, roughly equal to the number ...

Liquid water as a lone‐pair amorphous semiconductor

Abstract: We approximate liquid water as a lone‐pair amorphous semiconductor. Since electronic orbital times are short compared to the periods of atomic and molecular motion, properties dependent on electronic states can be interpreted to determine short‐time intermediate range order. An anomalous temperature dependence of the Urbach exponential absorption edge for intramolecular electronic excitation is noted and interpreted in terms of the perturbation of the lone‐pair valence band by hydrogen bonding. The extrinsic optical absorptions with I− and Br− doped water are observed to have Urbach tails. An approximate electronic band structure for pure and doped liquid water is presented.

Electron‐irradiation‐induced divacancy in lightly doped silicon

Abstract: Two electron traps—A2 and A3—produced in n‐type silicon by 1.5‐MeV‐electron irradiation are characterized by deep level transient spectroscopy. Activation energies of trapped majority carriers and capture cross sections for majority carriers at these levels are reported. From their production rates and annealing behaviors, they have been identified as different charge states of the same defect. Detailed annealing studies show that their annealing kinetics is first order with an activation energy of 1.47 eV. It is suggested that the defect is the divacancy and that dissociation is the likely process for its removal in these devices.

Photoelectronic properties of high‐resistivity GaAs : Cr

Abstract: The photoelectronic properties of high‐resistivity n‐type GaAs : Cr are quite similar to those of high‐resistivity n‐type GaAs : O described in the preceding paper. In the low‐temperature region, intrinsic photoconductivity is n type, increases exponentially with 1/T, and can be consistently described by a simple one‐level Shockley‐Read recombination model with a level lying 0.66 eV below the conduction band and a density that is remarkably constant over a variety of different materials. Two levels characteristic of the Cr doping lie at 0.86 eV below the conduction band and at 0.9 eV above the valence band. Low‐frequency photocurrent oscillations are associated with levels at 0.86 and 1.25 eV below the conduction band. The extrinsic photoconductivity at 0.86 eV is produced via two steps: (i) electrons are photoexcited from the ground state to the excited state of Cr+2 (d4) center, and (ii) they are then thermally excited to the conduction band.

Simple method of measuring drift-mobility profiles in thin semiconductor films

Abstract: A simple method of measuring drift-mobility profiles in semiconductor films is described. It is based on the low-frequency measurement of the transconductance and gate capacitance of an f.e.t. structure as a function of gate bias. Drift mobilities of 4000 to 5000 cm2/Vs have been measured on n-type GaAs films with 1016 to 1017 cm-3 doping levels.

Application of thermal neutron irradiation for large scale production of homogeneous phosphorus doping of floatzone silicon

Abstract: The limitations of conventional melt doping of phosphorus in silicon are discussed in relation to the obtainable homogeneity. Due to "theoretical-design" possibilities and increased manufacturing yield for power components based on n-type silicon, the method of thermal neutron irradiation doping has been developed for large scale production of floatzone silicon of homogeneous resistivity. It is shown that radioactivity problems do not interfere for resistivities above approximately 5Ω- cm and that lattice radiation defects can be annealed out to the extent that they appear harmless for all major applications. The doping homogeneity is discussed in view of the influencing nuclear reactor characteristics and the choice of starting material. Doping variations less than 1 percent across slices of up to 80-mm diameter are demonstrated to be obtainable with production results typically 3-10 percent. The minority carrier lifetime of neutron-doped silicon is shown to lie in the range of 100-1000 µs.

Field inversion control for n-channel device integrated circuits

Abstract: The field inversion properties of integrated circuits incorporating N-channel MOS devices are improved by using a silicon substrate whose bulk dopant concentration is low, but whose local dopant concentration is high at the field surfaces under the field oxide separating the active surface areas where the individual N-channel MOS devices are formed. The differential doping between surface areas under the field oxide and the active surface areas of the substrate is done by nonselectively ion-implanting boron into the substrate to form a uniform low resistivity layer, removing selected portions of the low resistivity layer to expose the unimplanted, high resistivity substrate and forming the active devices at the unimplanted substrate portions. As an option, the unimplanted surface portion can be doped to an intermediate dopant concentration to improve performance. The remaining pattern of the low resistivity layer is covered with field oxide. The invention allows the use of relatively inexpensive, low dopant concentration substrates to conveniently manufacture high performance N-channel MOS integrated circuits.

Substitutional doping in amorphous semiconductors the As-Si system

Abstract: The amorphous alloy system As-Si has been prepared in thin film form using the plasma decomposition of silane-arsine mixtures. Electrical and optical measurements show effects characteristic of sub...

Liquid‐phase epitaxial growth of 6H‐SiC by the dipping technique for preparation of blue‐light‐emitting diodes

Abstract: Epitaxial growth of 6H‐SiC has been carried out at 1500–1650 °C on 6H‐SiC substrates dipped into a Si melt in a graphite crucible. Epitaxial layers up to 100 μm thick have been deposited on the {0001} faces after 5 h growth. Layers grown on the Si faces at 1600 and 1650 °C have fairly flat and smooth surfaces. Undoped layers show n‐type conduction with a typical carrier concentration of 6.3×1017 cm−3 and mobility of 130 cm2/V sec at 300 °K. n‐ and p‐layers of higher carrier concentrations are obtained by the doping of nitrogen and aluminum, respectively. A p‐n junction is prepared in one growth run by an overcompensation procedure. Blue electroluminescence observed under the forward bias has enough brightness under room light at room temperature. The peak wavelength is 485 nm. The external quantum efficiency is 1.0×10−5 photons/electron at 300 °K.

Morphological and electrical properties of rf sputtered Y2O3‐doped ZrO2 thin films

Abstract: The structural, compositional, and electrical properties of rf sputter‐deposited Y2O3‐doped ZrO2 films have been investigated as a function of sputtering conditions. The results show that the application of an rf substrate bias during deposition has a large effect on both the morphological and electrical properties of the films. Auger electron spectroscopy, electron diffraction, and scanning‐electron‐fractography results show that films deposited at P=20 mTorr (2.67 Pa), VT=−500 V, and VS=−40 V are nearly stoichiometric, have a cubic crystal structure, and a relatively equiaxed microstructure. The results of electrical measurements indicate that films grown under these sputtering conditions have an ionic transference number which is nearly zero below 100 °C and rises to approximately 0.4 at 200 °C.

Schottky barrier semiconductor device and method of making same

Abstract: A first layer of semiconductor device is of doped amorphous silicon prepared by a glow discharge in a mixture of silane and a doping gas. The first layer is on a substrate having good electrical properties. On the first layer and spaced from the substrate is a second layer of amorphous silicon prepared by a glow discharge in silane. On the second layer opposite the first layer is a metallic film forming a surface barrier junction therebetween, i.e. a Schottky barrier. The first layer is doped so as to make an ohmic contact with the substrate. Preferably the doping concentration of the first layer is graded so the dopant concentration is maximum at the interface of the first layer and the substrate. In a second embodiment of the Schottky barrier semiconductor device an intermediate layer is between and contiguous to both the first layer and the substrate. The intermediate layer facilitates in making ohmic contact between the amorphous silicon and the substrate. Annealing and heat treating steps are performed in the fabrication of the Schottky barrier device to increase device efficiency.

Semi-Insulating Polycrystalline-Silicon (SIPOS) Films Applied to MOS Integrated Circuits

Abstract: A semi-insulating polycrystalline-silicon (SIPOS) film doped with oxygen atoms is deposited on the surface of silicon substrates by a chemical vapor reaction of silane and nitrous oxide in nitrogen ambient, and has been studied for the surface passivation of MOS-IC's, in particular, C/MOS-IC's of channel-stopperless structure. SIPOS films are semi-insulating and intrinsically neutral. A double-layer system consisting of 3000 A SIPOS and 6000 A SiO2 films is employed as a replacement of a thick silicon dioxide layer in C/MOS-IC's of channel-stopperless structure and exhibits excellent field-passivating properties, namely, a small drain-source leakage current, a high drain breakdown voltage, and a high parasitic threshold voltage. Furthermore, the silicon surface passivated by SIPOS films shows high stability under a severe bias-temperature stress. It is concluded that C/MOS-IC's passivated by SIPOS films are not required to have a channelstopper diffusion region and can be operated at high applied voltages, which leads to higher integrating density and higher reliability.

Differences between platinum- and gold-doped silicon power devices

Abstract: Both platinum and gold have been used to reduce lifetimes in fast recovery silicon power devices. There are substantial differences between the energy levels introduced by these impurities. Both impurities introduce acceptor levels which act to reduce hole lifetimes in n-type silicon; however, the gold acceptor is much deeper (E c - 0.54 eV) than the corresponding platinum acceptor (E c - 0.26 eV). In p-type material, on the other hand, the two impurities are quite similar; gold introduces a donor at E v + 0.35 eV, while the platinum donor is at E v + 0.32 eV. In terms of basic physics, this paper establishes guidelines to determine, for a given device type, which lifetime killer should be used to provide optimal performance. Platinum offers improved high-temperature properties and turn-on performance when compared to gold and is a better selection for devices which are switched so rapidly that the turn-off is governed mainly by the high injection lifetime. However, when the switching wave form involves low injection recombination tails, gold is a better choice than platinum.

Phosphorus doping of silicon by means of neutron irradiation

Abstract: Phosphorus doping of silicon with the aid of neutron irradiation is a very effective method to produce silicon single crystals with a homogeneous resistivity distribution and an exact average resistivity. The doping process is described and some aspects are given for the handling of the irradiated silicon. Experimental results concerning the resistivity distribution and the accuracy of aim are presented.

A study of the gold acceptor in a silicon p+n junction and an n-type MOS capacitor by thermally stimulated current and capacitance measurements☆

Abstract: The thermally stimulated current and capacitance responses of a gold doped p+n junction and n-type MOS capacitor were measured experimentally and modeled theoretically for the case of majority-carrier defect charging. The gold acceptor atoms are initially charged with electrons at low temperatures, and during the heating cycle, excess electrons are released from the gold atoms. The thermally stimulated current response for this phase is similar in both structures and has a distinctive peak-and-valley shape and an emission temperature about 220 K. During the steady-state phase, a current peak occurs in the MOS capacitance response. A physical model was developed and the influence of various parameters on the current and capacitance measurements was quantified. Various analytical schemes are described which allow rapid identification of the gold defect center and rapid computation of its density. A simple and inexpensive apparatus is described which is capable of heating rates as high as 10 K/s.

Complementary insulated gate field effect transistor structure and process for fabricating the structure

Abstract: A complementary insulated gate field effect transistor structure having complementary p-channel and n-channel devices in the same semiconductor substrate and a process for fabricating the structure incorporate oxide isolation of the active device regions, counterdoping of the p-well with impurities of opposite type to obtain a composite doping profile, reduction of Qss in the isolation oxide, doping of the gate and field oxides with a chlorine species and phosphorus doping of the polycrystalline silicon gates.

Method of doping inpurities

Abstract: In a method of doping impurities comprising mixing a carrier gas, a semiconductor compound gas and a doping gas and leading the mixed gas to a reaction chamber to form a semiconductor layer or a semiconductor oxide layer doped with impurities on a substrate inside the chamber, a part of the doping gas before mixing the doping gas with the other gases is taken and led to a gas analyzer and impurity concentration in the doping gas is monitored to control the impurity concentration in the doping gas.

Self-aligned epitaxial method for the fabrication of semiconductor devices

Abstract: In the fabrication of semiconductor devices, a method is provided which includes the steps of selectively doping a semiconductor substrate of one conductivity type to form therein discrete regions of opposite conductivity type, followed by selective epitaxial growth to fill the windows of the diffusion mask, whereby the epitaxially grown regions are inherently characterized by exact alignment with the doped regions. The self-aligned epitaxial structure is then subjected to further processing in accordance with numerous alternate schemes to provide a wide variety of devices.

Amorphous germanium as an electron or hole blocking contact on high-purity germanium detectors

Abstract: Experiments were performed in an attempt to make thin n/sup +/ contacts on high-purity germanium by the solid phase/sup 1)/ epitaxial regrowth of arsenic doped amorphous germanium. After cleaning the crystal surface with argon sputtering and trying many combinations of layers, it was not found possible to induce recrystallization below 400/sup 0/C. However, it was found that simple thermally evaporated amorphous Ge made fairly good electron or hole blocking contacts. Excellent spectrometers have been made with amorphous Ge replacing the n/sup +/ contact. As presently produced, the amorphous Ge contact diodes show a large variation in high-voltage leakage current.

Multilayer semiconductor switching devices

Abstract: The specification discloses semiconductor switching devices having more than five layers of alternating semiconductor conductivity types and which do not utilize substantial lateral switching currents during the operation thereof Ones of the exterior layers of the devices are heavily doped In one embodiment of the invention, an asymmetrical regenerative semiconductor switch is disclosed which operates in the general manner of a silicon controlled rectifier but which includes two blocking junctions therein In another embodiment of the invention, a semiconductor switching device having symmetrical switching operation is disclosed

Influence of Mn Impurity in Te-As-Ge-Si Glasses

Abstract: In order to investigate the roles and an incorporation scheme of impurities in amorphous semiconductors, electrical, optical and ESR measurements are carried out for Te48As30Ge10Si12 glasses doped with various amounts of Mn. A decrease of the electrical activation energy Ea and broadening of the optical absorption edge are caused by the introduction of Mn, while the optical gap does not change appreciably. An ESR signal with g=4.3 due to a small amount of Mn incorporated in the amorphous network is observed. The ESR center is explained by the double acceptor characteristic of Mn on the basis of the g-value and the magnitude of the hyperfine structure constant. It is concluded that the decrease of Ea is caused by the shift of the Fermi level EF due to holes supplied by the double acceptors. From the linear relation between the shift of EF and the center density of the ESR signal with g=4.3, the upper limit of the density of localized states around EF is estimated to be 1.5×1020 cm-3 eV-1.

Dislocation velocities and electronic doping in silicon

Abstract: Measurements of velocities of dislocations in silicon as a function of temperature and type of electronic impurity doping using Lang x‐ray topography are reported. Doping with n‐ and p‐type impurities results in an increase of the dislocation velocity and a decrease of the activation energy for both screw and 60° dislocations. The double kink nucleation and migration model of Gerk that takes kink motion to be limited by Auger electron‐hole recombination‐generation processes yields a satisfactory description of the experimental results.

Semiconductor Electrodes VII . Digital Simulation of Charge Injection and the Establishment of the Space Charge Region in the Absence and Presence of Surface States

Abstract: Transport of free carriers following charge injection to a semiconductor electrode is simulated. The relaxation of the free carrier results in the buildup of the space charge region whose properties are calculated. For an intrinsic semiconductor, the relaxation resembles that of the cations and anions in the diffuse double layer at a metal/electrolyt e interface following charge injection to the metal. For an extrinsic semiconductor, some additional specific effects arise, which are discussed. The effect of surface states is considered and the interaction of a surface level with the semiconductor bands is simulated. This interaction results in trapping of charge from the space charge region and delivery of it to the surface. The properties of the space charge region in the presence of surface states are calculated, and their effect on the relaxation process demonstrated. There has been much interest recently in semiconductor electrodes, and especially in photoeffects and photoelectrochemical experiments which may lead to devices of practical use, such as for solar energy utilization [see (1-3) and references therein]. Although the basic principles of the semiconductor electrode/electrolyte interface were formulated some time ago and have been reviewed extensively (4-8), the quantitative treatment of the behavior of semiconductor electrodes is quite complicated involving carrier diffusion and migration, thermal- and photogeneration, and recombination in the semiconductor itself in addition to the usual mass transfer and kinetic processes in the electrolyte phase and interphase charge transfer steps. Digital simulation methods (9, 10) have been very valuable in the treatment of complex kinetic or mass transfer problems in electrochemical systems. It is the aim of this paper and following ones in this series to apply digital simulation techniques to electrochemistry at semiconductor electrodes and the behavior of the semiconductor/el ectrolyte interface under illumination. In this paper we discuss the basic concepts of simulation of a semiconductor and the sequence of events following charge injection to a semiconductor electrode and leading to the formation of a space charge region. Following papers will describe the establishment of a photovoltage at an ideally polarized semiconductor electrode under steady illumination and the production of a photocurrent when charge transfer across the electrode/solution interface occurs.

Electrical properties of layered MoSe2 single crystals doped with Nb and Re

Abstract: Electrical properties of semiconducting MoSe2 single crystals doped with Re and with Nb are described. Impurity conduction can be characterized by three activation energies ∊1 > ∊2 > ∊3. At low temperature and for high doping levels a transition to a metallic state is observed. A band model is suggested which accounts for the measured activation energies and is in agreement with the photoemission results and optical data.

Electrical properties of vanadium pentoxide doped with lithium and sodium in the α-phase range

Abstract: The electrical conductivity and Seebeck coefficients have been measured from room temperature to 500° C for polycrystalline V2O5 and V2O5 doped with lithium and sodium in the α-phase range. The conductivity increases with doping and the energy of activation decreases. The Seebeck coefficient indicates that electrons are the majority carriers. The results have been discussed in terms of the two-level hopping model.