Resonance-like tunneling across a barrier with adjacent wells

We examine the behavior of transmission coefficient T across the rectangular barrier when attractive potential well is present on one or both sides and also the same is studied for a smoother barrier with smooth adjacent wells having Woods-Saxon shape. We find that presence of well with suitable width and depth can substantially alter T at energies below the barrier height leading to resonant-like structures. In a sense, this work is complementary to the resonant tunneling of particles across two rectangular barriers, which is being studied in detail in recent years with possible applications in mind. We interpret our results as due to resonant-like positive energy states generated by the adjacent wells. We describe in detail the possible potential application of these results in electronic devices using n-type oxygen-doped gallium arsenide and silicon dioxide. It is envisaged that these results will have applications in the design of tunneling devices.     

Giant injection magnetoresistance in the heterostructure gallium arsenide/granular film with cobalt nanoparticles

We have studied the electron transport and have observed new phenomenon—the positive injection magnetoresistance on heterostructures gallium arsenide/granular film SiO₂ with Co nanoparticles and gallium arsenide/granular film TiO₂ with Co island layers.     

Best candidate materials for fast speed response and high transmission performance efficiency of acousto optic modulators

An acousto-optic modulator (AOM), also called a Bragg cell, uses the acousto-optic effect to diffract and shift the frequency of light using sound waves (usually at radio frequency). They are used in lasers for quality switching, telecommunications for signal modulation, and in spectroscopy for frequency control. This paper has presented the best candidate selected acousto optic materials based AOM for upgrading speed response and transmission performance characteristics. These materials are common materials for acousto-optic devices such as silica glass (SiO₂), tellurium dioxide TeO₂), gallium phosphide, and gallium arsenide. As well as we have deeply investigated the important transmission characteristics of acousto optic modulators such as transmission performance efficiency, transmission bit rate, diffraction angle and efficiency, transient speed response, signal transmission quality, bit error rate and modulation bandwidth under wide range of the affecting parameters for different selected acousto optic materials to be the major of interest.     

Degradation of gallium arsenide under irradiation with an excimer laser

The results of a study of degradation of the surface of gallium arsenide resulting from irradiation with a power excimer laser at power densities ranging from the threshold power to the power level causing local melting of the surface are presented. Two degradation mechanisms have been identified, one of which causes the formation of a thin near-surface layer of modified nonstoichimetric gallium arsenide at a power level higher than 1×10⁷ W/cm² and the other of which causes the formation of a separate gallium phase. The formation of the separate gallium phase can be produced either by a single pulse of laser radiation with a power density exceeding 2.7×10¹¹ W/cm² or by a few less powerful pulses. An empirical relationship has been established between the power density and the number of pulses causing the formation of the separate gallium phase. It has also been established that as a result of laser irradiation at the boundary of “cold” and “hot” gallium arsenide, periodically ordered defects in the form of blocks aligned along the [100] directions emerge.     

Dislocations in GaAs single crystals grown by the Czochralski method

The influence was studied of growth conditions on the dislocation density in gallium arsenide single crystals grown by the Czochralski method from a gallium-enriched melt. Etching in a solution of 1 part cone. HNO₃ and 2 parts H₂O served to determine the dislocation density across and along a single crystal. The dislocation density along the crystal was found to depend mainly on the angle of crystal diameter increase.     

Optical and Magnetoacoustic Nonkinematic Data-Recording Devices

We demonstrate the possibility of constructing nonkinematic data-recording devices based on a special optical board with planar electrooptical lightguides and ultrasonic-signal storing in highly dispersed magnetic-striction polycrystalline ferrites. The efficiency of operation of planar electrooptical light guides made of cadmium sulfide and gallium arsenide is studied experimentally. The characteristics of information recording in spinel Ni_0.97-0.99Co_0.1-0.3Fe₂O₄ and garnet Y₃Fe_4.15Al_0.85O₁₂ are measured.     

Gallium arsenide optoelectronic IC's for computer networks

The physics of gallium arsenide offers distinct advantages compared to silicon for device applications based on mobility, epitaxial bandgap engineering, and optoelectronic function. Because of these advantages, compared to silicon, gallium arsenide transistors and optoelectronic devices are likely to be found in future computer systems. I first discuss material advantages and challenges for commercial realization of these applications. Examples of these potential applications in communication and computer systems are given. Highly integrated optoelectronic circuits will likely be found in optical links for data communications. The state of the art will be illustrated with recent results from a joint program that spans several IBM research and development laboratories. A demonstration of a compactly packaged gigabit per second optical data link with error rates low enough for computer communications has been made with two highly integrated MESFET chips and one laser array.     

Giant injection magnetoresistance in gallium arsenide/granulated film heterostructures with nanosize cobalt inclusions

Electron transport has been studied in the gallium arsenide/granulated SiO₂ film heterostructure with Co nanoparticles and in the gallium arsenide/TiO₂ film heterostructure with Co island sublayers. When electrons are injected from a film into a semiconductor, a new phenomenon is observed, which is called injection magnetoresistance. For the SiO₂(Co)/GaAs structure with 60 at. % Co in a magnetic field of 23 kOe at a voltage of 50 V, the injection magnetoresistance reaches 5200% at room temperature.     

Investigation of gallium arsenide containing coppee as a material for photoresistor receivers

The properties of gallium arsenide doped with copper are investigated for different modes of diffusion, as a material for the sensitive elements of a photoresistor IR receiver. The procedure for obtaining specimens with the required parameters is established, and the material obtained is used to manufacture photoresistors. The threshold sensitivity P_t of a photoresistor receiver with microwave bias based on gallium arsenide doped with copper reaches the values obtained in photoreceivers based on germanium doped with gold, but the GaAs:Cu photoreceiver has a more rapid response. The detection capability D^*of a GaAs:Cu photoresistor receiver with microwave bias considerably exceeds the values of D^* of a photoreceiver with a constant bias using the same material.     

Thermal stability of optical properties of electron-irradiated GaAs

We have studied the thermal stability of the secondary absorption in gallium arsenide which was irradiated with electrons. The annealing temperatures of a number of radiation defects have been determined. The charge state of the H₁-center has a significant influence on its thermal stability. Reasons are discussed for the differences in annealing properties of radiation defects based on capacitive properties and optical absorption.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 49–53, February, 1982.     

Controlling the nanodot formation on GaAs surface during focused ion beam processing

GaAs processed using gallium-focused ion beams for the fabrication of photonic devices mostly results in gallium nanodots on the surface. These gallium nanodots may produce unwanted effects and deteriorate the optical and electrical properties of the devices. We have investigated the FIB processing of GaAs with and without exposure to an insulator-enhanced etching precursor gas (XeF₂) to explore the use of XeF₂ during GaAs processing. It is reported that without the gas, FIB processing results in nanodots on the surface that vary in size and density depending on processing parameters such as incident energy, beam current, angle and dwell time. Processing with insulator (XeF₂)-enhanced etching gas irrespective of the process parameters eliminates the nanodots and results in a smooth surface, as characterized by scanning electron microscopy and atomic force microscopy. This method will be useful for surfaces which require dry processing without exposure to any wet chemical etching.     

Operation performance characteristics of vertical-cavity surface-emitting lasers (VCSELs) under high thermal neutron irradiated fields

To operate and read out even the innermost detectors under any particular conditions, electronics and optical components must be developed accordingly. For semiconductor lasers, on which we will concentrate here, it has been found that an inner temperature increase has a direct impact on the light power emitted by the device. It was found that the effects of radiation on the behavior of semiconductor lasers are convolved with those of temperature. An optimized coupling to the cooling of the laser device reduces the thermal effects in the material. Therefore, a test stand to qualify the effect of heat in the device and the adoption of the heat sink is realized. In this paper, we create a model describing the degradation of the light power and voltage characteristic of a semiconductor-laser undergoing irradiation where the high temperature effects are taken into account. This VCSEL-device model can be used to predict the behavior and operation-performance characteristics (rise time, 3 dB bandwidth, light power, resonance frequency, and transmission bit rate) of a laser being irradiated with different neutron doses. We check the robustness of the model against the high fluence (in excess of 10¹⁵ neutrons/cm²). We take into account the study of different semiconductor- and polymeric material-based VCSEL devices such as aluminum gallium arsenide (AlGaAs), indium gallium arsenide phosphors (InGaAsP), and polymeric polymethylmethacrylate (PMMA) under the same operating conditions.     

Calculation of the field dependence of nonradiative transition rate from the shape function of optical vibronic transition

An algorithm is suggested for calculation of field dependences of the emission rate from the shape function of the optical transition. Comparison with the experimental data obtained for the V _GaS_As complex in gallium arsenide showed that this algorithm is preferable compared to the methods based on the one-coordinate model.     

First principles study of the electronic and optical properties of GaAs nanoparticles under the influence of external uniform electric field

We present electronic and optical properties of the hydrogen terminated gallium arsenide nanoparticles using time dependent density functional theory (TD-DFT). The electronic and optical properties of the GaAs nanoparticles were calculated at presence of the uniform external electric field in the range from 0 to 0.51 V/Å. The induced electric filed can decrease the HOMO–LUMO gap of the nanoparticles and the mount of these reductions increases with gain of the electric field strength.     

Influence of Ga/(Ga + In) grading on deep‐defect states of Cu(In,Ga)Se2 solar cells

The benefits of gallium (Ga) grading on Cu(In,Ga)Se₂ (CIGS) solar cell performance are demonstrated by comparing with ungraded CIGS cells. Using drive‐level capacitance profiling (DLCP) and admittance spectroscopy (AS) analyses, we show the influence of Ga grading on the spatial variation of deep defects, free‐carrier densities in the CIGS absorber, and their impact on the cell's open‐circuit voltage V_oc. The parameter most constraining the cell's V_oc is found to be the deep‐defect density close to the space charge region (SCR). In ungraded devices, high deep‐defect concentrations (4.2 × 10¹⁶cm^–3) were observed near the SCR, offering a source for Shockley–Read–Hall recombination, reducing the cell's V_oc. In graded devices, the deep‐defect densities near the SCR decreased by one order of magnitude (2.5 × 10¹⁵ cm^–3) for back surface graded devices, and almost two orders of magnitude (8.6 × 10¹⁴ cm^–3) for double surface graded devices, enhancing the cell's V_oc. In compositionally graded devices, the free‐carrier density in the absorber's bulk decreased in tandem with the ratio of gallium to gallium plus indium ratio GGI = Ga/(Ga + In), increasing the activation energy, hindering the ionization of the defect states at room temperature and enhancing their role as recombination centers within the energy band. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Current-voltage characteristics of Au/GaN/GaAs structure

Au/GaN/n-GaAs structure has been fabricated by the electrochemically anodic nitridation method for providing an evidence of achievement of stable electronic passivation of n-doped GaAs surface. The change of the electronic properties of the GaAs surface induced by the nitridation process has been studied by means of current-voltage (I-V) characterizations on Schottky barrier diodes (SBDs) shaped on gallium nitride/gallium arsenide structure. Au/GaN/n-GaAs Schottky diode that showed rectifying behavior with an ideality factor value of 2.06 and barrier height value of 0.73 eV obeys a metal-interfacial layer-semiconductor (MIS) configuration rather than an ideal Schottky diode due to the existence of GaN at the Au/GaAs interfacial layer. The formation of the GaN interfacial layer for the stable passivation of gallium arsenide surface is investigated through calculation of the interface state density N_ss with and without taking into account the series resistance R_s. While the interface state density calculated without taking into account R_s has increased exponentially with bias from 2.2×10¹² cm⁻² eV⁻¹ in (E_c−0.48) eV to 3.85×10¹² cm⁻² eV⁻¹ in (E_c−0.32) eV of n-GaAs, the N_ss obtained taking into account the series resistance has remained constant with a value of 2.2×10¹² cm⁻² eV⁻¹ in the same interval. This has been attributed to the passivation of the n-doped GaAs surface with the formation of the GaN interfacial layer.     

Study of the Surface Processes in Vapor-Phase Epitaxial GaAs: Asymmetric Trapping of Atoms at the Step

Experimental proofs of asymmetric trapping of atoms at the growth step in vapor-phase epitaxy of gallium arsenide in the GaAs–AsCl₃–H₂ system are given. The data obtained confirm the important role of the surface diffusion mass transfer in the growth of epitaxial GaAs layers on vicinals in the neighborhood of (111)A. The effective diffusion length is estimated.     

Calculation of the field dependence of the rates of emission of carriers from deep centers based on an experimental form-function for the optical transition

An algorithm is proposed for calculating the field dependence of the emission rates based on a form-function for the optical transition. A comparison is made with experimental data for the V_GaS_As complex in gallium arsenide. This scheme for calculating the field dependence is found to be preferable to methods based on a single-coordinate model. Zh. éksp. Teor. Fiz. 116, 1027–1034 (September 1999)     

Electrical characteristics of nickel/gallium-arsenide barrier layer diodes

The voltage-current and voltage-capacitance characteristics of rectifier barriers obtained by electrochemical deposition of nickel on electronic gallium arsenide were studied. It turned out that the electrical properties of barrier layer diodes depend in large measure on the conditions of formation of the rectifier junction, on the charge carrier concentration in the semiconductor, and on the crystallographic orientation of its surface. Schottky-type barriers were obtained by appropriate treatment of the semiconductor surface.     

注硅半绝缘GaAs的深能级

用深能级瞬态谱(DLTS)详细研究了硅离子注入Liquid-encapsulated Czochralski(缩写为LEC)半绝缘GaAs的深中心。结果表明,在注硅并经高温退火的有源区中观测到4个多子(电子)陷阱,E₀₁,E₀₂,E₀₃和E₀₄。它们的电子表观激活能分别为0.298,0.341,0.555和0.821eV。其中E₀₄与EL2有关,但不是EL2缺陷。E₀₄的电子 关键词：