Self-compensation of carbon in HVPE-GaN:C

Abstract

Electrical properties of carbon-doped halide vapor phase epitaxy-GaN are presented and discussed. Crystals of the highest structural quality and with different carbon concentrations are investigated. Resistivity and Hall measurements as a function of temperature are analyzed in detail. It is found that the concentration of free holes systematically decreases with the increase of carbon concentration. Such behavior results from the fact that the compensation of the carbon acceptor level increases with the carbon concentration. It is accepted that carbon is amphoteric impurity in GaN, creating an acceptor as well as a donor state, which leads to self-compensation. The analysis of existing electron paramagnetic resonance results is extremely important. It enabled us to determine the compensation ratio as a function of carbon concentration. A combination of electron paramagnetic resonance, secondary ion mass spectrometry, and Hall data allowed us to conclude that the acceptor level (CN) exhibits rather significant temperature shift equal to 0.35 meV/K.