Calculation of the Probabilities of Nonradiative Transitions from Deep Impurity Centers with Account for Electron–Phonon Interaction

Using the form–function of optical transition as a basis, we suggest an algorithm for calculating the field dependences of the probability of nonradiative transitions. The algorithm worked out is compared with an experiment carried out for the V _Ga S _As complex in gallium arsenide. The conclusion is drawn that the proposed scheme of calculating the field dependences is preferable to the methods based on a single–coordinate model.     

Calculation of the probability of optical transitions in strong electric fields

An algorithm is proposed for calculating the spectrum of the cross section for photoionization of carriers on deep centers in electric fields on the basis of the form function of an optical transition.An experiment and calculations were performed for the complex V_Ga-S_As in GaAs. The proposed model is compared with theoretical works based on the single-coordinate approximation. It is concluded that the single-coordinate model is applicable for describing the field-dependence of the cross section for photoionization of an electron on a V_Ga-S_As center. Data on the influence of an external electric field on the change in the moments of the form function of the absorption band of the complex V_Ga-S_As in GaAs are obtained. It is concluded that an electric field influences the adiabatic potentials of the center investigated.     

Calculation of the Parameters of a One‐Coordinate Model of the VGaSAs and VGaSnGa Complexes in Gallium Arsenide

Experimental optical bands of the emitting complexes (a gallium vacancy with a donor at the nearest, from the vacancy, sublattice site) V_GaS_As and V_GaSn_Ga in GaAs are investigated in a wide temperature range. The parameters of a onecoordinate model of these centers are determined. A configurationcoordinate diagram of the V_GaS_As complex is constructed. Calculation of the field dependences of emission rates is carried out in terms of the parameters of the onecoordinate model of the V_GaS_As complex and the data obtained are compared with the results of experimental studies of the emission of electron holes from a deeplying center of the V_GaS_As complex.     

Isothermal capacitance transient spectroscopy (ICTS) study for midgap levels in Hb-GaAs by rapid thermal annealing

We studied the midgap levels by using isothermal capacitance transient spectroscopy (ICTS) in Hb-GaAs which had been processed by rapid thermal annealing (RTA). As the annealing time at 850 °C increased, the EL2 trap (E _c–0.81 eV) was transformed to the EX2 trap (E _c–0.73 eV) and eventually to the EX1 trap (E _c–0.87 eV). The diffusivity of the EL2 trap obtained from the experimental result of the heat treatment was about 1.02·10^–8cm²/s at 850 °C. This result indicate that the EL2 trap contains an interstitial arsenic atom. The result of the transformation to the EX1 and EX2 traps suggests that, when the EL2 trap is V_AsAS_iV_GaAs_Ga, the EX2 trap may be V_AsV_GaAs_Ga, which As_i is diffused out during a thermal annealing.     

On the validity of the amphoteric-defect model in gallium arsenide and a criterion for Fermi-level pinning by defects

Using the theoretically calculated point-defect total-energy values of Baraff and Schlüter in GaAs, anamphoteric-defect model has been proposed by Walukiewicz to explain a large number of experimental results. The suggested amphoteric-defect system consists of two point-defect species capable of transforming into each other: the doubly negatively charged Ga vacancyV _Ga ^2– and the triply positively charged defect complex (AS_Ga+V _As)³⁺, with As_Ga being the antisite defect of an As atom occupying a Ga site andV _As being an As vacancy. When present in sufficiently high concentrations, the amphoteric defect systemV _Ga ^2– /(As_Ga+V _As)³⁺ is supposed to be able to pin the GaAs Fermi level at approximately theE _v +0.6 eV level position, which requires that the net free energy of theV _Ga/(As_Ga+V _As) defect system to be minimum at the same Fermi-level position. We have carried out a quantitative study of the net energy of this defect system in accordance with the individual point-defect total-energy results of Baraff and Schlüter, and found that the minimum net defect-system-energy position is located at about theE _v +1.2 eV level position instead of the neededE _v +0.6 eV position. Therefore, the validity of the amphoteric-defect model is in doubt. We have proposed a simple criterion for determining the Fermi-level pinning position in the deeper part of the GaAs band gap due to two oppositely charged point-defect species, which should be useful in the future.     

电子顺磁共振“AsGa”的光淬灭行为与EL2亚稳态机理

根据Goltzene等人最近关于原生LEC,HB,压缩变形和中子辐照GaAs中电子顺磁共振(EPR)“As_Ga”谱低温光淬灭实验结果,结合Baraff和Schlüter最近关于EL2亚稳态的理论计算,本文认为可进一步证实作者之一在1981年提出的EL2(As_GaV_AsV_Ga)缺陷模型,同时还对Wager和Van Vechten最近提出的EL2(As_GaV_AsV_Ga)的亚稳态机理加以评述和修正。 关键词：     

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.     

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)     

Simulation of Transferred Electron Devices with Linearly Graded Composition of 3-5 Threefold Semiconductor in Active Zone

Two-level, displaced-maxwellian approach model of transfer electron effect in variband semiconductors has been created. With the help of the model research of TED based on variband semiconductor compounds In _x(z) Ga _1–x(z) As, Al _x(z) As, InP _1–x(z) Ga _1–x(z) As _x(z) has been done. Composition of the semiconductors x(z) in the active zone of TED depends linearly on the coordinate. It has been proved that work of TED with variband active zone is defined by dependence of relaxation frequency of electrons concentration in -valley upon coordinate. If the frequency is decreasing function dipole domains transit in the diode, but if the frequency is not decreasing function, so accumulation layers transit in the diode. Critical generation frequencies, power and frequencies characteristics of TED's based on semiconductor compounds In _x(z) Ga _1–x(z) As, Al _x(z) As, InP _1–x(z) Ga _1–x(z) As _x(z) have been defined.     

Comparison of the band alignment of strained and strain-compensated GaInNAs QWs on GaAs and InP substrates

We present a comparison of the band alignment of the Ga_1−xIn_xN_yAs_1−y active layers on GaAs and InP substrates in the case of conventionally strained and strain-compensated quantum wells. Our calculated results present that the band alignment of the tensile-strained Ga_1−xIn_xN_yAs_1−y quantum wells on InP substrates is better than than that of the compressively strained Ga_1−xIn_xN_yAs_1−y quantum wells on GaAs substrates and both substrates provide deeper conduction wells. Therefore, tensile-strained Ga_1−xIn_xN_yAs_1−y quantum wells with In concentrations of x0.53 on InP substrates can be used safely from the band alignment point of view when TM polarisation is required. Our calculated results also confirm that strain compensation can be used to balance the strain in the well material and it improves especially the band alignment of dilute nitride Ga_1−xIn_xN_yAs_1−y active layers on GaAs substrates. Our calculations enlighten the intrinsic superiority of N-based lasers and offer the conventionally strained and strain-compensated Ga_1−xIn_xN_yAs_1−y laser system on GaAs and InP substrates as ideal candidates for high temperature operation.     

Influence of the Substrate Orientation on the Silicon Capture into A- and B- Sublattices of Gallium Arsenide in Molecular Beam Epitaxy

The influence of crystallographic orientation of the growth surface near (100) and (111)A GaAs singular faces on the silicon capture into A- and B-sublattices of gallium arsenide in molecular beam epitaxy is investigated by the electrophysical and photoluminescence methods. It is demonstrated that the silicon dopand is incorporated into GaAs layers not only as simple Si_Ga donors but also as elemental Si_Ga acceptors and more complex defects, namely, Si_As–V_As complexes. The concentration of defects of different types in layers depends on the orientation of the growth surface, and the amphoteric properties of silicon on the (111)A face are manifested stronger than those on the (100) face.     

Prediction of enhanced ferromagnetism in (Ga,Mn)As by intrinsic defect manipulation

In the diluted magnetic semiconductor (Ga,Mn)As the excess of As incorporated as As antisites (As_Ga) is responsible for the hole compensation. The As_Ga defect can be transformed into a As interstitial–Ga vacancy pair (As_i–V_Ga) upon illumination. In this paper we study the effects of such a transition on the ferromagnetism of (Ga,Mn)As using density functional theory within the local spin density approximation. We find that the ferromagnetic order in (Ga,Mn)As is strongly enhanced if As_Ga are transformed into As_i–V_Ga pairs, since the hole compensation is reduced. This suggests a valuable way to tune the carrier concentration and hence the T_c in (Ga,Mn)As, without changing the Mn concentration nor the microscopic configuration of the Mn ions.     

Defects in as-grown and annealed AlxGa1−xAs single crystals

Photoluminescence studies were made on Sn-, Te- and Ge-doped Al_xGa_1-xAs single crystals before and after annealing at 800°C for 21 h in evacuated and sealed quartz ampoules. The thin p-type surface layer, which was present on all nondegenerate n-Al_xGa_1-x As crystals after annealing, is attributed to the introduction of Si from the inner wall of the ampoule to form shallow Si_As and V_As-Si_As acceptor defects. Sn_As, V_Ga-Te (or) V_Al-Te), Ge_As and V_As-Ge_As defects were observed in Sn-, Te- and Ge-doped Al_x Ga_1-xAs after annealing. The defects were identified by plotting their characteristic recombination radiation energies versus Al composition x and comparing with previously established assignments in GaAs (x = 0). Two prominent bands, located at 1.53 and 1.46 eV independent of Al composition x, were detected in annealed (p) Al_xGa_1-xAs: Ge. The exact nature of the defects giving rise to these bands is not known.     

Far-infrared spectra of Pb1−xMnxTe alloys

Far-infrared reflectivity spectra of Pb_1−xMn_xTe (0.0001x0.1) single crystals were measured in the 10–250 cm⁻¹ range at room temperature. The analysis of the far-infrared spectra was made by a fitting procedure based on the model of coupled oscillators. In spite of the strong plasmon–LO phonon interaction, we found that the long wavelength optical phonon modes of these mixed crystals showed an intermediate one–two mode behavior.     

Energy band gaps for the GaxIn1−xAsyP1−y alloys lattice matched to different substrates

A pseudopotential formalism within the virtual crystal approximation in which the effects of composition disorder are involved is applied to the Ga_xIn_1−xAs_yP_1−y quaternary alloys in conditions of lattice matching to GaAs, InP and ZnSe substrates so as to predict their energy band gaps. Very good agreement is obtained between the calculated values and the available experimental data for the alloy lattice matched to InP and GaAs. The alloy is found to be a direct-gap semiconductor for all y compositions whatever the lattice matching to the substrates of interest. The (Γ→Γ) band-gap ranges and the ionicity character are found to depend considerably on the particular lattice-matched substrates suggesting therefore that, for an appropriate choice of y and the substrate, Ga_xIn_1−xAs_yP_1−y could provide more diverse opportunities to obtain desired band gaps, which opens up the possibility of discovering new electronic devices with special features and properties.     

X射线吸收谱对Ga0.946Mn0.054As薄膜中缺陷的研究

采用低温分子束外延法(LT-MBE)制备出Ga_0.946Mn_0.054As稀磁半导体(DMS)薄膜.通过X射线吸收谱(XAS)研究影响Ga_0.946Mn_0.054As薄膜性质的主要缺陷Mn间隙原子(Mn_I)和As反位原子(As_Ga).实验结果表明,在较低生长温度(T_S=200℃)下Ga_0.946Mn_{0.054 关键词： 0.946}Mn_0.054As稀磁半导体')" href="#">Ga_0.946Mn_0.054As稀磁半导体 X射线吸收谱 As反位缺陷 Mn间隙原子     

Using positron 2D-ACAR as a probe of point defects in GaAs: The As vacancy as a case study

Two-Dimensional Angular Correlation of positron Annihilation Radiation (2D-ACAR) experiments have been performed on n-type GaAs. By combining these results with those from positron lifetime experiments, the momentum distribution of the arsenic vacancy in its neutral (V _aAs ⁰ ) and negative (V _As ^– ) charge states have been extracted. These distributions were all normalized to the respective positron lifetime that characterizes them. The first thing to be noticed is that the momentum distributions of the vacancies, as seen by the positron, are fairly isotropic and structureless. The distribution forV _As ⁰ is more peaked than that ofV _As ^– while the latter is more intense in the large momentum regions of the spectra. From this, it can be inferred that VA. has a smaller open volume thanV _As ⁰ A closer look at the momentum distribution of the vacancies reveals that they are not entirely isotropic, but, in fact, have a bulk-like component. Finally, the experimental results for bulk GaAs andV _As ^– compare well in a qualitative manner with the momentum distributions that result from an ab-initio molecular dynamics calculation.     

Analysis of the stability of semiconducting five-component solid solutions of III-V compounds

The model of regular solutions has been used to obtain expressions for calculating the boundaries of the region of spinodal decomposition for five-component solid solutions of III-V compounds. The stability region of the solid solution Al_x1Ga_x2In_1–x1–x2P_yAs_1–y has been estimated.Moscow Institute of Electronic Engineering. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 11–13, December, 1993.     

Solubility and point defect-dopant interactions in GaAs—II: Tin-doping

The form of the solubility curves for tin in both LPE and VPE grown GaAs are rationalised by a thermodynamic model which presumes that the dominant acceptor state due to tin is the donor-gallium vacancy complex Sn_GaV^?_Ga rather than the commonly postulated Sn^?_As.In LPE growth from tin-rich solutions where the arsenic concentration in the melt exceeds the gallium concentration, very low electron mobilities have been reported and this is shown to arise from auto-compensation of the Sn⁺_Ga donors by the Sn_GaV^?_Ga acceptors.