Effect of asymmetric Schottky barrier on GaN-based metal-semiconductor-metal ultraviolet detector

An asymmetric Schottky barrier metal-semiconductor-metal (MSM) ultraviolet (UV) detector with Ni/GaN/Au structure was designed and the effect of the asymmetric Schottky barrier on the detector response was investigated. This detector had response at 0 V bias and increased responsivity when a positive bias was applied to the Ni/GaN contact; however, the internal gain disappeared when a negative bias was applied to this point. This contrasts with a symmetric Ni/GaN/Ni Schottky barrier MSM UV detector which had no internal gain under positive/negative bias and almost no response at 0 V bias. The improved performance of the asymmetric Schottky barrier detector was because of the lower work function of Au causing reduction of Schottky barrier and hence enhancing a hole-accumulating and trapping process, which resulted in internal gain. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3672030]