Numerical analysis of charge carriers injection in a light emitter or detector device based on a metal-semiconductor-metal structure

Abstract

Modern metal-semiconductor-metal nano- and micro-structures exhibit unique properties related to both light emission and detection. Here we develop a novel optimized numerical model to calculate charge carrier density inside a n-type semiconductor micro-crystal that is sandwiched between two Schottky contacts. We use drift-diffusion equations and finite difference methods and utilize the Scharfetter-Gummel discretization technique. We demonstrate that the concentration of majority charge carriers in the semiconductor can be reduced below the level observed at zero applied bias by surpassing the current density of minority charge carriers beyond that of the majority charge carriers. Subsequently, minority charge carrier concentration increases and becomes the dominant charge carrier inside the semiconductor at high applied bias. In addition, we provide evidence that the open circuit voltage of a semiconductor under illumination occurs at the point where the minority-majority current densities intersect. By adjusting the Schottky contact barrier, the crossing potential between minority and majority carriers can be controlled, thereby allowing for manipulation of the open circuit voltage. This is an important factor in determining the density of trap states in the semiconductor and designing an open circuit voltage photodetector. We verify our results using COMSOL Multiphysics software and show that our numerical approach is found to be more time-efficient than the methods employed by COMSOL Multiphysics.