V. V. Zelenin

Growth and investigation of epitaxial 6H-SiC layers obtained by CVD on Lely-grown substrates

The aim of the present work was: (1) to grow SiC epilayers on Lely-grown 6H-SiC substrates (characterized at present by the highest crystalline perfection) and (2) to investigate the quality of the epilayers. The growth of the SiC epitaxial layers was performed in the system SiH4-CH4-H2. It was found that the crystal perfection of the on-grown epilayers is not much less than that of the Lely substrate. To study the electrical properties of the obtained epitaxial layers, Schottky barriers were formed on their surfaces with the use of various metals. In layers grown on sublimation- and hydrogen-etched substrates, the concentration Nd-Na was ~ 6 × 1016 − 3 × 1017 cm−3 The thickness of the intermediate region between substrates and epilayers was smaller than 0.01 μm.

Investigation of 6H–SiC site competition epitaxy the silane–methane–hydrogen gas system

Abstract The homoepitaxial growth of 6H–SiC layers has been performed using methane and silane as active gas sources. Voltage–capacitance measurements and results of i-DLTS spectroscopy characterized the epilayers. In accordance of the C/Si ratio in the gas phase the epitaxial layers exhibit n- or p-type conductivity. The dependence of N D − N A or N A − N D = F (Si/C) in unintentionally doped layers is, as we suggest, connected with structural defects.

Growth and Study of Thick 3C-SiC Epitaxial Layers Produced by Epitaxy on 6H-SiC Substrates

3C-SiC epitaxial layers with a thickness of up to 100 μm and area of ~0.3-0.5 cm2 have been grown by sublimation epitaxy on hexagonal (6H-SiC) substrates at a maximum growth rate of about 200 μm per hour. The epilayers obtained are of n-type (Nd-Na ~ 1017 -1018 cm-3). According to X-ray data, the epitaxial layers are composed of the 3C-SiC polytype, without inclusions of other polytypes. The donor-acceptor (Al-N) recombination band with hνmax ~ 2.12 eV predominates in the photoluminescence (PL) spectrum. A detailed analysis of a PL spectrum measured at 6 K is presented. A conclusion is made that the epitaxial layers can be used as substrates for electronic devices based on 3C-SiC.

High temperature silicon carbide stabilitrons for the voltage range from 4 to 50 V

Abstract Voltage stabilitrons based on 6H-SiC p-n structures produced by the open-system sublimation technique have been fabricated. Stabilization voltages were in the range 4–50 V. Operating currents were from 1 to 100 mA. Differential resistance was in the range 10–20 Ω at 100 mA current. Upper ambient temperature was 300 °C.

Absorption spectra of bulk aluminum nitride crystals doped with Er3+ ions

This Letter presents results of analysis of the absorption spectra of AlN:Er3+ bulk crystals. In the spectral of 370–700 nm, absorption lines responsible for intraconfiguration electron transition from the ground state 4I15/2 to the excited states of Er3+ ions are found. Transitions to the levels of the 4F9/2, 2H11/2, and 4G11/2 states at 2 K are studied in detail. The number of observed lines for these transitions fully agrees with that theoretically possible for f–f electron transitions in Er3+ ions found in a noncubic crystal field. The small width of the observed lines and their number indicate that erbium ions displace mostly one regular crystal position. Most probably, Er3+ occupies the position of Al. Energy positions of excited states for the considered transitions are determined.

The effect of surfactants on epitaxial growth of gallium nitride from gas phase in the Ga-HCl-NH3-H2-Ar system

We have studied epitaxial layers of gallium nitride (GaN) in a template composition grown by surfactant-mediated hydride-chloride vapor phase epitaxy. The surfactant component was provided by 5 mass % additives of antimony and indium to the source of gallium. Comparative analysis of the obtained results shows evidence of the positive influence of surfactants on the morphology of epitaxial GaN layers.

The effect of hydrogen etching on the electrical properties of autoepitaxial silicon carbide layers

Experimental data showing that preliminary hydrogen etching of a SiC substrate influences the concentration of donors or acceptors in autoepitaxial SiC layers are presented. The impurity concentration in the epitaxial layers grown on etched and unetched substrates may differ by an order of magnitude. A physical explanation of the observed correlation is proposed. The importance of the effect of competitive etching on the epitaxial growth is pointed out.

Some aspects of SiC CVD epitaxy

A brief comparative analysis of techniques for the CVD epitaxy of SiC is made. Two tendencies in the use of inner reactor equipment are distinguished. Irrespective of the design features and the active gases used, chemical reactions of hydrogen with the interior of the reactor occur concurrently with the epitaxial growth. These reactions control the actual [C]/[Si] ratio in the gas phase and in part determine the background impurity concentration in pure epilayers.

Local thermoelectric effects in wide-gap semiconductors

Experimental confirmation of the appearance of local thermal electromotive forces, which were previously found in structures based on silicon p–n junctions, is obtained. The current–voltage and frequency characteristics of an asymmetric potential barrier at the GaN/Mg boundary and of a p–i–n structure based on GaAs are studied. It is shown that, similarly to wide-gap semiconductors, the contribution of local thermal electromotive forces determines the features of the current–voltage characteristics and the frequency features of the current–power characteristics, in particular the Gaussian resonance. Proper account and use of local thermoelectric forces makes it possible to attain a drastic increase in the efficiency of thermoelectric conversion and an improvement in the operating parameters of microelectronic components.

Effect of neutron irradiation on current-voltage characteristics of packaged diodes based on 6H-SiC pn structures

Neutron irradiation (~1 MeV, dose 1014-5.6∙1015 neutron/cm2) of packaged diodes based on 6H-SiC pn structures (with the base n-layer doped to ~5∙1016 cm-3) has been studied. In addition to the well-known rise in the series resistance of the diodes, the effect of a partial suppression of the excess current in both forward-and reverse-biased diodes and that of an increase in the recombination current, probably associated with the decrease in the nonequilibrium carrier lifetime, were discovered and discussed. These effects are common to 6H-and 4H-SiC pn structures.