Radiative recombination of holes in delta-p-doped gallium arsenide

Photoluminescence spectra of δ-p-doped GaAs structures of different doping levels are studied experimentally. It is found that set of PL bands observed in δ-p-doped samples recently is regularly broadened with doping concentration increase due to appearance of additional low-energy bands and their subsequent red shift at higher doping levels. A red shift of the bands and a change of their relative intensities were caused also by excitation laser intensity decrease and/or temperature increase. These results confirm our previous assumption that the bands are due to radiative recombination of spatially separated photoelectrons with holes occupying size-quantization levels of δ-layer potential well.     

Anomalous PL brightening caused by partial Auger recombination of a (D, X) complex during an impact ionization avalanche in n-GaAs

Partial Auger recombination of the (D⁰, X) bound-exciton in n-GaAs at 4.2 K during an impact ionization avalanche under an applied pulse voltage has been investigated. The bright photoluminescence (PL)-pattern observed by applying the pulse voltage, characterizes well the formation of a current density filament. The observation of the bright PL spectra inside the current density filament gives a quite new result concerning the partial Auger recombination process of the (D⁰, X) complex, leaving the neutral donor in the excited states.     

Rapid thermal process-induced recombination centers in ion implanted silicon

This work presents direct evidence for a correlation between rapid thermal process-induced recombination centers and co-implanted metallic impurities in ion implanted silicon. Experimental evidence includes the dose dependence of the minority carrier diffusion length measured by the SPV technique, SIMS and RBS analysis of high-dose implantations which show the presence of heavy metals, the dependence of the final diffusion lengths on the mass of the implanted ions, as well as the successful modification of an implantation equipment.     

Near band-edge luminescence of semi-insulating undoped gallium arsenide at high levels of excitation

The dependences of the maximum and the half-width of near band-edge photoluminescence of semi-insulating undoped-GaAs crystals at 77 K on the concentration of background acceptor impurities and the level of excitation in the range from 3×10²¹ to 6×10²² quantum/(cm² s) are investigated. The observed dependences are explained by formation of the density tails of states as a result of fluctuations of impurity concentration and participation of localized states of the donor impurity band in radiative transitions. Reduction of many-particle interaction at increasing of N can be connected with increasing of shielding of charge carriers by atoms of impurity.     

Chemical etching of p-type Si(lOO) by K2Cr2O7

Chemical etching of the (100) face of p-type Si by aqueous K₂Cr₂O₇ was investigated with a contactless transient photoconductivity method, i.e. the time-resolved microwave conductivity (TRMC) method, after ns laser pulse excitation and with XPS, UPS, and LEED. TRMC transients after etching show a much slower decay that is explained by a decrease of surface recombination velocity. XPS indicates the formation of a mixed oxide of Si^III and Cr^v. During heating to 600°C this layer first transforms to a Si^IV-Cr^III oxide. After heating to 1200°C the oxide and Cr at the surface have disappeared, as indicated by UPS (He I and He II) and LEED (sharp 2×1 LEED pattern). However, XPS still shows the presence of Cr^o which evidently is diffused into the bulk. This can also be deduced from the transient photoconductivity measurements as TRMC transients at this stage show a fast decay rate that must be due to an increased bulk decay rate of excess charge carriers.     

Transient photoluminescence decay study of minority carrier lifetime in GaAs heteroface solar cell structures

Transient photoluminescence decay has been studied theoretically and experimentally as a technique for the investigation of GaAs solar cell materials and solar cell structures. The time-dependent continuity equation was solved using two variable boundary conditions modelling the interface between the emitter and hetero-window layer (AlGaAs) and between the emitter and space charge region, respectively. The solution was found with help of the Fourier transform method and the method of residues. There results an analytical expression for the time dependent photoluminescence (PL) intensity. The influence of various solar cell parameters on this photoluminescence transient has been studied in detail. An experimental investigation of transient PL decay was performed using a synchronously pumped mode locked and cavity dumped Nd:YAG/dye laser system for excitation and an optical sampling oscilloscope as the detector. GaAs wafers with and without surface passivation have been measured as well as hetero-window pn-structures and processed solar cells. A fit of the theoretical PL transients to the measured transients allows surface and bulk recombination parameters to be determined.Dedicated to H.-J. Queisser on the occasion of his 60th birthday     

Semiconducting structures and devices based on gallium arsenide with deep centers

We have examined the characteristics of nontraditional gallium arsenide -v-n type device structures, in which p-n junctions are formed by doping the semiconductor with deep centers. The properties of -v-n structures are established by processes of charge trapping at deep centers under the effect of an external bias or exposure to a wide spectral range of electromagnetic radiation. The nature of formation of S-type negative differential resistance for a reverse biased -v-n structure and the mechanism of high speed switching (with a switching time of (0.4–5)×10^–10 sec) were analyzed. The results of an investigation of the effects of optical radiation, x-rays, -radiation and high energy charged particles on the structures are discussed and the characteristics of new devices constructed using -v-n structures are presented. These devices include high speed avalanche S-diodes and triodes, wide spectral band photodiodes (=0.2–10 µm) and detectors for x-rays, -radiation, and relativistic electrons.V. D. Kuznetsov Siberian Physical-Technical Institute, State University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 33–44, September, 1992.     

Enhanced photoluminescence from gallium arsenide semiconductor coated with Au nanoparticles

We demonstrate a method for improving photoluminescence of gallium arsenide semiconductor by simply coating a thin layer of Au nanoparticles on its surface. Further focused ion beam bombardment at the sputter-coated Au film was conducted to control the size, the distribution, and the morphology of the Au nanoparticles via the changes of the focused ion-beam irradiation conditions. Photoluminescence of GaAs coated with the Au nanoparticles with average size of 5 nm in diameter is enhanced to about threefold relative to that of pure GaAs. Numerical calculations were conducted based on finite-different time-domain method. Results indicated that the enhancement is mainly attributed to the contribution of local surface plasmon resonance of Au nanoparticles.     

Direct recognition of non-radiative recombination centers in semi-insulating LEC InP:Fe using double excitation photoluminescence

In order to observe the effect of intra-band gap excitation on the photoluminescence (PL) properties of undoped InP and iron doped InP (InP:Fe), PL measurements were performed in InP crystals with thickness of 360 μm and area of about 4×3 mm², grown by the liquid encapsulated Czochralski (LEC) technique upon excitation with both Ar-ion laser and 980 nm light. The PL intensities for InP:Fe under 980 nm wavelength light illumination relative to no illumination increased by about 52%, 33%, and 12% for the 1.337, 1.380, and 1.416 eV peaks, respectively, at 10 K, whereas there was no illumination effect for undoped InP. This is a strong indication that Fe centers play a role as non-radiative recombination centers to decrease the PL intensity. PL experiments were performed in the spectral range of 1320-1440 meV for InP in the sample temperature range of 10-160 K. The electron and hole photoionization cross-sections at 980 nm wavelength light illumination were calculated as and , respectively.     

Arsenic growth on the gallium arsenide surface during oxidation

Crystalline arsenic was observed to grow on the surface of GaAs during exposure to continuous-wave laser radiation. A study of the time development of the arsenic growth as revealed by Raman backscattering indicated that a surface diffusion process was responsible for limiting the growth process. Temperature measurements were performed from which the diffusion barrier energies were obtained for various GaAs samples. From these results the diffusion process was shown to depend on the Fermi level of the sample.     

Ferromagnetism in epitaxial layers of gallium and indium antimonides and indium arsenide supersaturated by manganese impurity

We report on laser synthesis of thin 30–200 nm epitaxial layers with mosaic structure of diluted magnetic semiconductors GaSb:Mn and InSb:Mn with the Curie temperature T_C above 500 K and of InAs:Mn with T_C no less than 77 K. The concentration of Mn was ranged from 0.02 to 0.15. In the case of InSb:Mn and InAs:Mn films, the additional pulse laser annealing was needed to achieve ferromagnetic behavior. We used Kerr and Hall effects methods as well as ferromagnetic resonance (FMR) spectroscopy to study magnetic properties of the samples. The anisotropy FMR was observed for both layers of GaSb:Mn and InSb:Mn up to 500 K but it takes place with different temperature dependencies of absorption spectra peaks. The resonance field value and amplitude of FMR signal on the temperature is monotonically decreased with the temperature increase for InSb:Mn. In the case of GaSb:Mn, this dependence is not monotonic.     

Plasma reflection in gallium arsenide

Procedures recently proposed for determining electrophysical parameters of highly doped semiconductors from the IR reflection spectra are analyzed. The case of n-type GaAs is discussed. Optical and Hall measurements have been carried out for a few samples, and it has been found that the electron density determined from the optical measurements is in good agreement with the Hall values, while the mobilities may differ significantly. It is concluded that mechanical polishing causes problems.Translated from Izvestiya VUZ. Fizika, No. 10, pp. 65–69, October, 1969.     

Hole injection and surface state effects at gallium arsenide electrodes

We report capacitance and luminescence measurements at gallium arsenide electrodes in 1 M H₂SO₄ electrolyte that indicate the injection of holes on cathodic polarization. The steady-state potential-current relations and photoeffects are reviewed critically. We show that the assumption of hole injection is equally plausible to that of electron extraction provided the surface recombination velocity is fast compared to the bulk diffusion and recombination process. In addition to the space charge there is a substantial surface charge of the type commonly observed at III–V semiconductor surfaces.     

Influence of gallium arsenide surface treatment in selenium vapors on subsurface defects

Influence of GaAs surface treatment in selenium vapors on the parameters of electronic states in the subsurface GaAs regions is investigated by the methods of volt-ampere and volt-farad characteristics and isothermal capacitance relaxation at temperatures in the interval 77–400 K. Electrophysical measurements of the Schottky barriers formed on the GaAs surface treated in selenium indicate a decrease in the surface electron state (SES) density and unfastening of the Fermi energy level. In this case, generation of subsurface defects is observed that causes compensation of shallow donors and refastening of the Fermi energy level typical of some structures.