B. Arnaudov

Donor-acceptor pair emission enhancement in mass-transport-grown GaN

A dominating donor-acceptor pair (DAP) emission at about 3.27 eV is observed in the photoluminescence and cathodoluminescence spectra of intentionally undoped mass-transport (MT)-grown GaN, while only a weak presence of the DAP emission is recorded in the as-grown hydride vapor phase epitaxial GaN. A comparative study of impurity and native defect incorporation in the as-grown and MT GaN was performed, showing a significant increase of oxygen and empty clusters involving Ga vacancy and oxygen in the MT GaN. Based on the observed results as well as on doping analysis of the structure and kinetic analysis of the emission intensities, we propose an acceptorlike complex, creating a state as a semiclassical potential well near the valence-band top due to the local tensile strain caused by the empty clusters to be responsible for the dominating behavior of the DAP emission.

Electron mobility in heavily doped gallium arsenide due to scattering by potential fluctuations

The electron mobility in heavily doped GaAs is calculated by using an approach by Yussouf and Zittartz (1973) to account for the electron scattering in a Gaussian random potential. The cases of random and correlated impurity distribution are considered. Comparison with experimental data gives evidence that correlation is essential for the electron transport. It gives rise to a weak dependence of mobility on the electron concentration, which agrees very well with experiment.

Free electron recombination in degenerately doped and moderately compensated gallium arsenide

The room-temperature, band-edge photoluminescence spectra of degenerately doped (n=1, 2, 3, 8, 10*1019 cm-3) and compensated (K=0.05, 0.1, 0.2, 0.3, 0.5) samples have been investigated for identification of the radiative recombination mechanism and to analyse the possibility for a quantitative estimation of the Burstein-Moss shift. The measured spectra consist of two emission bands. The high-energy band (band-edge luminescence) predominates in intensity over the impurity-associated emission band. The spectral shape is discussed in accordance with theoretical ideas that it follows the free electron energy distribution. The calculated curves (over the full range of electron concentration) are in good agreement with the experimental spectra.

Magnetic-field-induced localization of electrons in InGaN/GaN multiple quantum wells

We study longitudinal electron transport in InGaN/GaN multiple quantum wells (MQWs) at moderate magnetic fields. We observe a stepwise behavior of both the Hall coefficient and magnetoresistivity. The peculiarities are explained by a magnetic-field-induced localization of electrons in a two-dimensional (2D) potential relief of the InGaN MQW due to composition fluctuations. We extend the model for a magnetic localization of electrons, treating every QW like a quasi-2D system with a cylindrical potential relief. The calculated values of the decrease of the sheet electron concentrations in a magnetic field based on such an assumption for 2D density of states in a InGaN MQW system are in good accordance with the experimentally obtained values.

Sublinear impurity solubility in indium phosphide and gallium arsenide epitaxial layers

Abstract The solubility curves of tellurium donors in InP and GaAs liquid phase epitaxial layers, as well as germanium and zinc acceptors in GaAs and InP, respectively, are studied on the basis of impurity and native defect equilibria. In a wide doping range our results are in good accordance with calculated solubility dependences. The influence of vacancies in both sublattices on the impurity incorporation is taken into account. As a result, a sublinear donor and nearly linear acceptor solubility occurs, depending on the vacancy-to-impurity concentration ratio.

ELECTRON TRANSPORT IN SB-DOPED METALORGANIC EPITAXIAL GAAS GROWN AT MODERATE AS-RICH CONDITIONS

The influence of antimony incorporation in GaAs metalorganic vapor phase epitaxial (MOVPE) layers has been investigated. The results obtained concern the behavior of the carrier concentration (n) and the mobility (μ) developed from Hall effect measurements. In order to achieve a reliable quantitative interpretation the samples studied have been grown at a moderate V/III ratio which ensures n‐type conductivity and does not favor SbGa heteroantisite defect formation. Three regions of specific influence of Sb doping on the electrical parameters have been distinguished. For Sb mole fraction in the input gas phase (MFTMSb) ranging between 0 and 6×10−6, n slightly decreases, while the mobility sharply increases compared with undoped layers. This is discussed in terms of electrically active and neutral As vacancies. The quantitative consideration of the scattering mechanism offers the possibility of correcting the compensation ratio in the undoped GaAs samples determined by commonly used procedures. The n and μ ...

Effect of carrier concentration on the microhardness of GaN layers

The paper presents a microhardness study of thick crack-free hydride vapor phase epitaxial GaN layers (not intentionally doped), and of thin metal-organic vapor phase epitaxial (MOVPE) GaN layers (undoped and Si-doped), grown on sapphire. A Vickers indentation method was used to determine the microhardness under applied loads up to 2 N. An increase in the microhardness was observed with decreasing carrier concentration and increasing mobility. A dip at an indentation depth of about 0.75 μm is observed in the microhardness profile in the MOVPE films, and is correlated with peculiarities in the spatially resolved cathodoluminescence spectra. The relationship between the mechanical and electrophysical parameters is discussed.

Hall effect data analysis of GaN n(+)n structures

We develop a model for analysis of Hall effect data of GaN structures composed of sublayers with different thicknesses and contacts placed on the top surface, We analysed the contributions of the c ...

Modeling of the Light Emission Spectra of InGaN/GaN Quantum Well with Highly Doped Barriers

We investigate light emission spectra at different excitation levels of nanoscale thin InGaN film participating in an InGaN/GaN quantum well (QW) with heavily doped barriers for green and blue light emitting diodes (LEDs). We model the spectral shape and energy position in frames of the free electron recombination model created first for highly doped 3D direct gap III-V semiconductor films and applied for QWs at low excitation. The model accounts for the influence on the potential width of the QW of the random impurity potential of the doped barriers which penetrates into the QW. The blue shift at high excitation is supposed to be due to the filling of the conduction band with degenerate 2D nonequilibrium electrons. A structure in the emission bands is observed and it is assumed to be a result from step-like 2D density-of-states (DOS) in the QW. A good agreement is obtained between the calculated and experimental spectra assuming that the barriers are graded.

On the nature of the near bandedge luminescence of InN epitaxial layers

Based on the behaviour of the energy position and shape of the photoluminescence (PL) spectra of InN layers versus electron concentration, and on the theory of the PL emission in degenerate semiconductors, we separate the spectra into three main groups. As a consequence the near band edge luminescence was interpreted as being dominated by: (i) recombination of electrons from the bottom of the conduction band to shallow acceptor levels in low doped InN; (ii) free‐to‐bound radiative recombination (FBRR) of degenerate electrons from the conduction band with nonequilibrium holes located in the valence band tails in moderately doped InN and (iii) FBRR with a blue shift due to pushing‐up of nonequilibrium holes over the thermal equilibrium level in the valence band tails in highly doped InN.