On Injection in Intrinsic Single-Carrier Devices

TL;DR

This paper analyzes how injection barriers affect space-charge-limited currents in single-carrier devices, providing conditions based on device parameters to optimize device design for accurate measurements.

Contribution

It introduces simple, parameter-dependent conditions to predict when injection barriers limit current in single-carrier devices, aiding device design.

Findings

Injection barriers depend on temperature, permittivity, and film thickness.

Conditions for injection limitation align with previous observations.

Guidelines for designing devices to avoid injection-limited measurements.

Abstract

By considering the changes in the interface charge-carrier densities of a single-carrier device as a function of injection-barrier heights and comparing these to the equilibrium, background charge-carrier density of a device with Ohmic contacts, we calculate simple conditions for when these barriers are expected to limit injection and therefore significantly affect space-charge-limited currents in the device. We show that these conditions depend on the device temperature, semiconductor relative permittivity, and effective density of states, but most importantly the thickness of the semiconducting film being probed. This is in accordance with previous observations and similar derived expressions for when defects influence single-carrier devices. The conditions described herein can be used to aid the design of single-carrier devices for space-charge-limited current measurements that are not limited by injection.