Study of the Abnormally High Photocurrent Relaxation Time in α-Ga2O3-Based Schottky Diodes

Ga 2 O 3 is a wide-bandgap material with a number of unique characteristics that make it a promising material for photonics: it is optically transparent to optical and near-ultraviolet radiation and has a high breakdown voltage and high radiation resistance. One of the shortcomings that currently prevent the use of this material in solar-blind photodetectors is the anomalously long rise and decay time of photoconductivity, which can reach hundreds of seconds. Such a slowdown of the photoconductivity significantly limits the application area of these materials. The nature of this effect is studied. The rise and decay times of the photoinduced current in α-Ga 2 O 3 Schottky diodes grown by the HVPE method on sapphire are measured under LED illumination at 259 and 530 nm. Under exposure to ultraviolet radiation, the current through the photosensitive structure of two opposing diodes increases in three stages: a very fast increase with a characteristic time of 70 ms, a slow increase with a characteristic time of 40 s, and a prolonged decay with a characteristic time of ~300 s. Upon subsequent illumination with green radiation, the increase in current with a characteristic time of 130 and 40 s is superimposed on a slow decrease in the amplitude of the maximal current with a characteristic time of ~1500 s. The analysis of the current relaxation shows the presence of deep centers with an energy of E C = 0.17 eV. A significant slowdown in the relaxation of the photoinduced current can be associated with potential fluctuations near the Schottky barrier.