Photoassisted tunneling from free-standing GaAs thin films into metallic surfaces

TL;DR

This study investigates photoassisted tunneling from free-standing GaAs thin films into gold, analyzing how bias, distance, and light power affect photocurrent, and compares results with a comprehensive theoretical model.

Contribution

It introduces a model accounting for bias-dependent barrier height and surface recombination effects, explaining experimental tunneling photocurrent behaviors.

Findings

Conduction band tunneling dominates over surface states.

Bias dependence of photocurrent varies with tunnel distance.

Surface recombination effects are significant at small tunnel distances.

Abstract

The tunnel photocurrent between a gold surface and a free-standing semiconducting thin film excited from the rear by above bandgap light has been measured as a function of applied bias, tunnel distance and excitation light power. The results are compared with the predictions of a model which includes the bias dependence of the tunnel barrier height and the bias-induced decrease of surface recombination velocity. It is found that i) the tunnel photocurrent from the conduction band dominates that from surface states. ii) At large tunnel distance the exponential bias dependence of the current is explained by that of the tunnel barrier height, while at small distance the change of surface recombination velocity is dominant.