PROPERTIES OF A PHOTOVOLTAIC DETECTOR BASED ON AN N-TYPE GAN SCHOTTKY-BARRIER

In this article, we report on the characterization of a photovoltaic d etector based on an n-type GaN Schottky barrier. We first present the photovoltaic responsivity above the gap. Its spectrum is explained by the combined effects of absorption and diffusion. The hole diffusion l ength is estimated to be in the 0.1 mu m range with a numerical model. The photoresponse below the gap is also investigated and it is shown that the current generated by the internal photoemission is the major contribution to the photocurrent at reverse biases at 80 K. At room te mperature, an additional component to the photocurrent is clearly demo nstrated and identified. This extra current stems from the existence o f traps. Several spectroscopy techniques are used to characterize thos e traps. The supplementary current emitted from the traps in the deple tion region accounts for the spectral and the temporal behavior of the Schottky photodetector at room temperature. (C) 1997 American Institu te of Physics.