Direct Observation of the Stretching of the Photoinduced Current Relaxation in α-Ga2O3 Schottky Diodes

Relaxation of photoinduced current in alpha-Ga2O3-based Schottky diodes was measured. Such Schottky diodes were fabricated using alpha-Ga2O3 films grown by Halide Vapor Phase Epitaxy (HVPE) on basal plane sapphire. Their photosensitivity in UV-C region was very high and several orders of magnitude higher than for visible light. The photoinduced current rise and decay times are found to be quite long, which is attributed to the hole capture by deep acceptors and to the effects of potential fluctuations. Due to these problems the photoinduced current relaxation process consists of several steps and takes more than hundreds of seconds. The characteristic relaxation times were calculated using the logarithmic differential analysis that demonstrated that the build-up and decay processes can be accurately described by stretched exponents with different broadening factors beta. It was shown that additional illumination by long-wave light can help to observe the slowing of the relaxation speed. The temperature activation energies for photoinduced current decay and rise times are 0.37 +/- 0.03 eV and 0.06 +/- 0.005 eV respectively.