E. A. Popova

Photoionization cross sections of E levels in electron-irradiated n-type GaAs

The spectral shape of the photoionization cross sections of E1-E3 levels and the low-energy part of the photoionization cross sections of E4, and E5 levels are determined. It has been shown that radiation defects with which these levels are associated are characterized by a strong lattice relaxation of magnitude ≈0.5 eV. The red absorption edge for these levels in p-type GaAs has been found to lie at photon energies greater than Eg (except, possibly, level E5).

Long-wave optical absorption in electron-bombarded GaAs

The absorption spectra of n- and p-type GaAs bombarded with 2-MeV electrons at T=300‡K were studied in the spectral range from 0.2 eV to Eg. It was found that “shallow” radiation-defect levels ≈Ec − 0.01 eV and ≈Ec + (0.06−0.1) eV were formed. The “structureless” character of the absorption in the region hΝ < Eg in electron-bombarded gallium arsenide specimens was shown to be due to the distinctive features of photoionization of deep levels and the strong electron-phonon interaction in this material.

Investigation of the electrical and photoelectric properties of manganese-doped gallium arsenide as a material for photoresistive detectors

An investigation was made into the electrical and photoelectric properties of gallium arsenide with an initial electron density 5×1015−4×1017 cm−3 doped with Mn in different thermodynamic diffusion regimes characterized by diffusion temperatures of 900 and 1000°C and arsenic vapor pressure 10−2 and 10−3 atm. The ionization energy and defect concentration were determined by a computer analysis of the equilibrium hole density determined from the Hall effect. Centers with ionization energy 0.08–0.10 eV were found, their concentration varying from 2×1019 to 2×1020 cm−3 depending on the diffusion temperature and the doping level of the original crystals. Data obtained by investigating the stationary intrinsic photoconductivity were used to determine a hole lifetime of tp 10−9 sec. The photoconductivity spectra were investigated in the range 0.5–2 eV at 77°K, and defects with ionization energy Ev + 0.6 eV were found in all samples. The impurity photoconductivity at wavelength 10.6 μm was investigated. It was shown that GaAs∶Mn can be used as a material for impurity photoresistors.

Behavior of copper in gallium arsenide with high tin concentration

Investigations were made of the electrical properties, the cathodolumiescence and photoconductivity spectra, and the temperature dependence of the majority carrier lifetime in gallium arsenide with a high concentration of tin (n=2·1018 cm−3, 1.5·1017 cm−3) that was doped with copper under different diffusion regimes. Measurements of the Hall effect revealed centers with an ionization energy 0.175 ± 0.005 eV, their concentration depending on the rate of cooling of the samples. The cathodoluminescence and Hall effect data suggest that the cathodoluminescence band observed at 1.35 eV in GaAs∶Sn∶Cu is associated with radiative transitions of electrons to centers with εa=Ev + 0.175 eV. The hole lifetime in GaAs∶Sn∶Cu has a complicated temperature dependence which can be explained qualitatively by the presence of two types of capture center.

Behavior of copper in gallium arsenide with a high tellurium concentration

The electrophysical properties and cathode luminescence spectra of gallium arsenide with a high tellurium concentration (n = 2·1018 cm−3) alloyed with copper are investigated under different diffusion conditions. Centers are determined from measurements of the Hall effect with an ionization energy of 0.190 ± 0.006 eV whose concentration does not depend on the arsenic vapor pressure (0.1 and 1 atm) and the cooling rate of the samples from the diffusion temperature. A band with hνm = 1.30–1.32 eV whose intensity depends on the cooling conditions of the samples was observed in the cathode luminescence spectra of these samples. The nature of the observed defects is discussed.

Investigation of the electrophysical and photoelectric properties of diffused layers of gallium arsenide obtained by compensation of copper

The distribution of the electrophysical and photoelectric properties of diffuse layers of p-GaAs obtained by doping copper using different diffusion modes is investigated. The properties of diffuse layers of p — n structures and volume specimens doped with copper over the whole depth are compared. The behavior of impurity centers is studied in these specimens and their effect on the electrophysical and photoelectric parameters of the material is investigated.

Selection of the model of an impurity energy spectrum of a semiconductor by the method of optimizing the parameters of the neutrality equation

Certain regularities are established which permit tracing the influence of the second level on the results of computing impurity center parameters by means of the results of an analysis of the log p(1/T) curve by using a “one-level” model. It is shown that the value of the impurity center degeneration factor can be the criterion for correspondence between the model selected and the true energy spectrum of the semiconductor.

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 Pt 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.

Electrophysical properties of heat-treated gallium arsenide

The electrical conductivity, Hall effect, ionization energy, and defect concentration of GaAs samples subjected to various forms of heat treatment were studied. The original material comprised single crystals grown by the Bridgman and Czochralski methods with electron concentrations of 2·1015−7·1017 cm−3. The ionization energy and defect concentration were calculated with an electronic computer. The thermal conversion of GaAs was attributed to traces of copper, lattice defects, and residual impurities. The mobility varied in a complicated manner with the temperature of heat treatment in GaAs samples retaining their original n-type conductivity.

Determining the parameters of local centers in a semiconductor from equilibrium charge-carrier concentration using a computer

A method of determining the parameters of local centers through the experimental dependence of charge carrier concentration on temperature is presented. The search algorithm for optimal parameter value as employed with a computer is developed. The method is verified by analysis of the experimental function p(T) for germanium and gallium arsenide specimens.