Asymmetric semicircular and triangular electrode structures to increase photo-to-dark-current ratio in MgZnO metal semiconductor metal photodetectors

Abstract

The effects of asymmetric semicircular and asymmetric triangular Schottky barriers on the current–voltage (I–V) characteristics of MgZnO metal semiconductor metal (MSM) photodetectors (PDs) have been investigated using a two-dimensional (2D) physical model based on the drift-diffusion theory. At a bias of 5 V, compared with the symmetric rectangular Schottky barrier MgZnO MSM PD, the dark current of the asymmetric semicircular and triangular Schottky barrier MgZnO MSM PDs is reduced by a factor of 15 for each electrode structure. On the other hand, the photocurrents of these asymmetric semicircular and asymmetric triangular PDs are enhanced by factors of 1.2 and 2, respectively. On the basis of these I–V characteristics, the highest photo-to-dark-current ratio (PDR) of 7294 is achieved in the asymmetric triangular Schottky barrier MgZnO MSM PD. In addition, the PDR can be increased further by optimizations, such as the incorporation of different metals to provide a higher asymmetry. The results show that the design of the asymmetric semicircular and asymmetric triangular Schottky barriers on the MgZnO MSM PDs is a promising method for applications requiring a low power and a high PDR.