Improved Efficiency of Photoconductive THz Emitters by Increasing the Effective Contact Length of Electrodes

TL;DR

This study demonstrates that surface patterning of SI-GaAs photoconductive emitters significantly enhances THz radiation by increasing electrode contact length, leading to over twofold improvements in emitted electric field amplitude.

Contribution

The paper introduces a novel surface patterning technique that increases electrode effective contact length, thereby improving THz emission efficiency in photoconductive emitters.

Findings

Electric field amplitude of THz pulses increased by over 2 times.

Surface patterning enhances electrode contact length and THz emission.

Patterned surface improves emitter performance without additional complex fabrication.

Abstract

We study the effect of a surface modification at the interface between metallic electrodes and semiconducting substrate in Semi-Insulating GaAs (SI-GaAs) based photoconductive emitters (PCE) on the emission of Tera-Hertz (THz) radiation. We partially etch out 500 nm thick layer of SI-GaAs in grating like pattern with various periods before the contact deposition. By depositing the electrodes on the patterned surface, the electrodes follow the contour of the grating period. This increases the effective contact length of the electrodes per unit area of the active regions on the PCE. The maxima of the electric field amplitude of the THz pulses emitted from the patterned surface are enhanced by up to more than a factor 2 as compared to an un-patterned surface. We attribute this increase to the increase of the effective contact length of the electrode due to surface patterning.