Electrical characterization and optical deep-level transient spectroscopy of autodoped GaN:C with various carbon concentrations

Abstract

We investigated the electrical and deep-level electronic properties of carbon-doped GaN (GaN:C) crystals. Three GaN:C samples with carbon concentrations of 1 × 1017, 1 × 1018, and 1 × 1019 cm−3 were prepared by controlling the growth temperature in an autodoping process during metalorganic vapor-phase epitaxy. To evaluate these properties, current–voltage (I–V), capacitance–voltage (C–V), and optical deep-level transient spectroscopy (ODLTS) measurements were performed. The I–V curves exhibited diode-like behavior, with leakage current and ideality factor varying systematically with carbon concentration. Under light emitting diode illumination, a significant increase in capacitance was observed, particularly in the more heavily doped samples. ODLTS measurements revealed multiple trap-related peaks with activation energies ranging from 0.20 to 0.90 eV. These results indicate that carbon-related defects and their charge transition levels vary with doping concentration, demonstrating that the carbon autodoping method enables systematic control over deep-level electronic states in GaN.