Surface properties of semiconductors from post-illumination photovoltage transient

TL;DR

This paper develops a model to analyze the transient surface photovoltage response of semiconductors after illumination, enabling better characterization of their electronic properties and extending the applicability of Kelvin probe methods.

Contribution

The paper introduces a new model for the temporal behavior of surface photovoltage, improving the analysis of fast-responding semiconductors beyond previous logarithmic decay assumptions.

Findings

The decay is only approximately logarithmic.

The model extends Kelvin probe applicability to faster semiconductors.

Results enable better characterization of semiconductor layers and nanowires.

Abstract

Free surfaces of semiconductors respond to light by varying their surface voltage (surface band bending). This surface photovoltage may be easily detected using a Kelvin probe. Modeling the transient temporal behavior of the surface photovoltage after the light is turned off may serve as a means to characterize several key electronic properties of the semiconductor, which are of fundamental importance in numerous electronic device applications, such as transistors and solar cells. In this paper, we develop a model for this temporal behavior and use it to characterize layers and nanowires of several semiconductors. Our results suggest that what has previously been considered to be a logarithmic decay is only approximately so. Due to the known limited frequency bandwidth of the Kelvin probe method, most previous Kelvin-probe-based methods have been limited to slow responding semiconductors. The model we propose extends this range of applicability.