High-performance metal-semiconductor-metal InGaN photodetectors using CaF2 as the insulator

Abstract

The authors report on the high-performance metal-semiconductor-metal (MSM) photodetectors (PDs) fabricated on high-quality InGaN film by introducing a superwide bandgap calcium fluoride ( CaF 2 ) as the insulator. The dark current of the PDs with CaF 2 is drastically reduced by six orders of magnitude compared with those without CaF 2 , resulting in an extremely high discrimination ratio larger than 10 6 between ultraviolet and visible light. The responsivity at 338 nm is as high as 10.4 A/W biased at 2 V, corresponding to a photocurrent gain around 40. The CaF 2 layer behaves as an excellent insulator for the InGaN-based MSM-PDs in dark condition, while it allows the electron injection through the metal/semiconductor interface under ultraviolet illumination, contributing to the photocurrent gain without sacrificing the response time ( ∼ ms ) .