Optical Writing and Electro-Optic Imaging of Reversible Space Charges in Semi-Insulating CdTe Diodes

TL;DR

This paper demonstrates how optical beams can reversibly manipulate and image space charges in semi-insulating CdTe diodes, enabling control of electric fields for improved radiation detector performance.

Contribution

It introduces a novel optical doping method to reversibly control space charges and electric fields in CdTe diodes, supported by real-time imaging and numerical simulations.

Findings

Optical doping induces stable, reversible space charges in CdTe diodes.

Real-time electric field imaging is achieved via the Pockels effect.

Numerical simulations confirm the role of deep levels in charge control.

Abstract

Deep levels control the space charge in electrically compensated semi-insulating materials. They limit the performance of radiation detectors but their interaction with free carriers can be favorably exploited in these devices to manipulate the spatial distribution of the electric field by optical beams. By using semi-insulating CdTe diodes as a case study, our results show that optical doping functionalities are achieved. As such, a highly stable, flux-dependent, reversible and spatially localized space charge is induced by a line-shaped optical beam focused on the cathode contact area. Real-time non-invasive imaging of the electric field is obtained through the Pockels effect. A simple and convenient method to retrieve the two-dimensional electric field components is presented. Numerical simulations involving just one deep level responsible for the electrical compensation confirm the experimental findings and help to identify the underlying mechanism and critical parameters enabling the optical writing functionalities.