快速热处理对应变InGaAs/GaAs单量子阱激光二极管电子发射和DX中心的影响

研究分子束外延(MBE)生长的应变In0.2Ga0.8AsGaAs折射率梯度变化异质结单量子阱激光二极管的快速热处理(RTA)效应.结果表明,RTA移除了InGaAsGaAs界面非辐射中心,提高77K光致发光效率和有源层电子发射.同时Al和Ga原子互扩散,也增加了AlGaAs波导层DX中心浓度.RTA处理后样品电流冲击老化实验证明DX中心浓度呈现出相应的增加.这表明DX中心可能是激光二极管性能退化的原因之一. 关键词： 量子阱 快速热处理 电子发射 DX中心     

The influence of the DX center on the capacitance of schottky barriers in n-type AlGaAs

The significance of both the density N, and the apparent built-in voltage V_a, as usually obtained from C-V measurements on Schottky barriers containing DX centers, is clarified. It is also shown that, owing to the non-equilibrium occupancy of the DX center, at low temperature the electron density in the flat-band region depends on the cooling rate of the sample.     

Si DX centers in GaAs at large hydrostatic pressures

A number of experimental and theoretical studies indicate that DX centers in GaAs, its alloys and other III–V semiconductors have negative U properties. Using far infrared localized vibrational mode (LVM) spectroscopy of Si donors in GaAs under large hydrostatic pressure in a diamond anvil cell we have discovered an LVM of the Si DX center. From the ratio of the LVM absorption lines of Si_Ga and Si_DX and the compensation in our GaAs samples, we show unambiguously that two electrons are trapped when the ionized shallow Si donors transform into negatively charged DX centers, in full agreement with the negative U model.Dedicated to H.-J. Queisser on the occasion of his 60th birthday     

High pressure and deep donors (DX centers) in gaas and algaas

Abstract

The presented paper is a review of some interesting phenomena characteristic for the DX center — a metastable donor in GaAs and AlGaAs. We concentrate on a presentation of microscopic models of the DX centers and their consequences. We point out some controversies concerning the nature of this donor impurity and the profits resulting from the wide use of pressure methods in resolving these controversies.     

AlGaAs∶Sn中DX中心电子俘获势垒的精细结构

采用定电容电压法,测量了n型Al026Ga074As∶Sn中DX中心电子热俘获瞬态,以及不同俘获时间后的电子热发射瞬态;并对瞬态数据进行数值Laplace变换,得到其Laplace缺陷谱(LDS).通过分析LDS谱,确定了电子热俘获和热发射LDS谱之间的对应关系,从而得到热俘获系数对温度依赖关系,以及与Sn相关的DX中心部分电子热俘获势垒的精细结构;通过第一原理赝势法计算表明,Sn附近的AlGa原子的不同配置是电子热俘获势垒精细结构产生的主要原因     

New class of holographic materials based on CdF<Subscript>2</Subscript> semiconductor crystals with bistable centers. I. Role of covalence in the formation of bistable centers

Calculations of the electronic structure of In, Ga, and Al impurity centers in a CdF₂ crystal in the cluster approximation using the method of scattered waves are made. The first two impurities form in additively colored crystals bistable centers having a ground two-electron (deep) state and a metastable hydrogen-like (shallow) state. A change in the nature of the chemical bond on doping a crystal with these impurities is traced, which consists in a considerable increase of its covalent component. A change for deep In and Ga centers is shown to be caused by the reconstruction of centers in their ground state, and a conclusion about the character of reconstruction is made. This conclusion agrees with recent calculations made for the center structure using the pseudopotential method. Conditions of formation of bistable centers in CdF 2 and their structure in different charge states are discussed.     

Effect of Coulomb correlations in a variable-valence impurity system and phonon drag on the thermoelectric constants in two-dimensional systems

The temperature behavior of the longitudinal Nernst-Ettingshausen coefficient in 2D systems is studied theoretically taking account of phonon drag and Coulomb correlations in a system of mixed-valence impurities at low temperatures. It is shown that the effect changes sign at the transition from entrainment to scattering by a correlated system of impurity centers. A sign change does not occur in the case of scattering by randomly distributed impurity centers. This temperature behavior of the Nernst-Ettingshausen coefficient is due to the radical rearrangement of the impurity system as a result of strong Coulomb correlations present in a system of impurities with mixed valence. As a result, the character of the scattering of charge carriers by the correlated system of charge centers changes substantially. Fiz. Tverd. Tela (St. Petersburg) 40, 553–556 (March 1998)     

Sulfur doping of AlN and AlGaN for improved n‐type conductivity

Achieving high levels of n‐type conductivity in AlN and high Al‐content nitride alloys is a long standing problem; significant decreases in conductivity are observed as the Al content is increased, a phenomenon that has been attributed to donors such as oxygen or silicon forming DX centers. We address this problem through a comprehensive first‐principles hybrid density functional study of potential n‐type dopants, identifying S_N and Se_N as two elements which are potential shallow donors because they do not undergo a DX transition. In particular, S_N is highly promising as an n‐type dopant because it also has a low formation energy and hence a high solubility. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Resistivity and Tensoresistive Characteristics of TlInSe2–CuInSe2 Solid Solutions

Technical Physics - The concentration dependences of the resistivities and tensosensitivity factors of Ti1 –xCuxInSe2 alloys from TlInSe2–CuInSe2 system have been studied in...     

Donor impurities and DX centers in the ionic semiconductor CdF2

Group-III impurities in the wide-gap ionic crystal CdF₂ are examined. After being heated in a reducing atmosphere, crystals with these impurities acquire semiconductor properties, which are determined by electrons bound in hydrogen-like orbitals near an impurity. Besides these donor states, nontransition impurities form “deep” states accompanied by strong lattice relaxation, i.e. they are strongly shifted along the configuration coordinate. These states are a complete analog of DX centers in covalent and ionic-covalent semiconductors. The difference of the behavior of nontransition impurities from that of transition and rare-earth impurities is analyzed. This difference is attributed to the character of the filling of their valence shells by electrons. A deep, multilevel analogy is drawn between the properties of deep centers in typical semiconductors with an appreciable fraction of a covalent bond component and in predominantly ionic crystal CdF₂ with semiconductor properties. Fiz. Tverd. Tela (St. Petersburg) 39, 1050–1055 (June 1997)     

Optical properties of the surface transition-metal structures in fluoride ionic crystals and peculiarities of their formation during thermal diffusion

The possibility of forming surface films with an elevated concentration of an impurity metal during high-temperature diffusion has been analyzed for a wide series of ionic crystals: LiF with Co, Ni, Mg, Ca, Ba, and Sr impurities; NaF with Co, Mn, Mg, Ca, and Sr; MgF₂ with Co and Ni; and CaF₂ with Co. It is established that films are formed only on alkali halide crystals with impurities of transition metals and are not formed on alkaline earth fluorides with transition metals, as well as on alkali halide crystals activated with other divalent cationic impurities. The dynamics of the increase and decrease in the intensity of centers related to impurity-vacancy dipoles during thermal diffusion is shown. The mechanisms of film formation are explained in terms of the features of growth and structure of ionic crystals with cationic impurities and on the basis of isomorphism rules.     

Ⅲ-Ⅴ族化合物半导体中的深能级杂质缺陷

本文综述了近十多年以来对Ⅲ-Ⅴ族化合物半导体中深能级杂质缺陷的研究工作。讨论了深能级杂质缺陷对Ⅲ-Ⅴ族化合物材料与器件的性能的重要影响。介绍了结谱法、光致发光与电子自旋共振等几种研究深中心的方法在研究Ⅲ-Ⅴ族化合物时的某些特点。评述了对砷化镓、磷化镓和磷化铟及某些Ⅲ-Ⅴ族混晶中的一些深中心所取得的研究成果。     

Negative persistent photoconductivity in GaAs (δ-Sn) structures

The effect of illumination with various wavelengths λ (770 nm<λ<1120 nm) on the conductivity of GaAs structures with tin δ-doping of the vicinal faces was investigated in the temperature range 4.2–300 K. Negative persistent photoconductivity was found in strongly doped samples. It was shown on the basis of the results of investigations of the Hall and Shubnikov-de Haas effects that the negative photoconductivity is due to a large decrease in the electron mobility with increasing electron density. The decrease of electron mobility is explained by ionization of DX centers, which destroys the spatial correlation in the distribution of positively charged donors and negatively charged DX centers. Zh. éksp. Teor. Fiz. 116, 2130–2139 (December 1999)     

Resonant DX centers in highly doped Sn-Ga1−xAlxAs under hydrostatic pressure in magnetic field

We report experimental evidence of deep impurity states producing a localized resonance in the Γ_1c band continuum in highly doped Sn-Ga_1−xAl_xAs. At low temperatures and increasing pressure, electrons were transferred from the Γ_1c band to the deep Sn donor state; this transfer of carriers was directly related to the pressure dependence of Shubnikov de Haas oscillations. Persistent photoconductivity, due to the DX nature of this deep level, was observed through the increase in the Γ carrier density resulting from illumination with a light emitting diode. This is interpreted as a photoionization of the DX centers up to the Γ_1c valley.     

Photoconductivity of gallium arsenide irradiated with 5 MeV protons

Several levels which develop in GaAs before and after proton irradiation were derived from the photoconductivity spectra. It is assumed that the majority of the levels which are observed after irradiation are related to uncontrollable impurities or to impurities which are activated during irradiation. The GaAs Cu samples were used to show that it is possible to activate admixtures by proton irradiation. It was established that the absolute photoconductivity is reduced during irradiation by the development of recombination centers. The average activation energy of these centers was estimated at 0.06 eV. Lattice defects are the recombination centers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 34–40, February, 1972.     

薄膜太阳电池的研究进展

介绍了薄膜太阳电池在光伏技术中的位置,详细叙述了非晶硅,铜铟锡,碲化镉等主要薄膜太阳电池的基本结构,制造方法,研究进展和现状,指出了存在的关键问题和解决的途径,并介绍了薄膜太阳电池的发展趋势和应用前景。     

Model of DX-like impurity centers in PbTe(Ga)

A new model is proposed for DX-like impurity centers, which are responsible for the Fermi-level stabilization and long-term relaxation effects in IV-VI semiconductors doped with group III elements. The model is based on the idea of a variable valence of the impurity, whereas the nature of the long-term effects at low temperatures is associated with the formation of an effective barrier caused by a change of two units in the impurity valence upon photoexcitation. The model is applied to an analysis of the photoconductivity spectra in PbTe(Ga). The model can also be applied to the classical DX centers in III-V semiconductors.     

Parameters of a multicomponent laser-induced plasma

Technical Physics - We report on the results of analysis of parameters of a laser-induced plasma, which were obtained using emission diagnostics of a laser torch plasma from a CuInSe2...     

Mobility of electrons upon scattering by a multicomponent correlated system of impurity centers

A system that contains two sorts of impurity centers spatially distributed in a random way is considered. Not all impurities of the first sort are ionized, and all the impurities of the second sort are ionized. Spatial correlations in the system of impurity ions of the first sort are investigated under conditions when the correlation radius of an impurity ion is limited from above due to a deficit of neutral impurities. The influence of randomly spatially arranged small-sized donors (impurities of the second sort) on correlations in the system of impurity ions is analyzed. The equations for describing the effect of small-sized donors on correlations in the system of impurity ions are obtained. The electron mobility at zero temperature is calculated by the example of HgSe: Fe (the correlated system of impurity centers consists of iron atoms and small-sized donors whose concentration is higher than the Mott concentration).     

Diffusion under periodic-supersaturation conditions during cyclic heat treatment

Conclusions The materials in which a tendency toward pore formation is observed during cyclic heat treatment are supersaturated with impurities at the low temperature of the cycle. The maximum supersaturation occurs in regions in which there is a high diffusion coefficient, particularly along grain boundaries. The impurities precipitated in these regions serve as crystallization centers for impurity diffusion from other regions. The pore formation can be thought of as the expansion of such regions and the enrichment of these regions with impurities and vacancies.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 11, pp. 126–128, November, 1970.