Improved efficiency of photoconductive THz emitters by increasing the effective contact length of electrodes

Abhishek Singh,Harshad Surdi,S S Prabhu,V V Nikesh,G H Döhler

doi:10.1063/1.4842615

Abhishek Singh, Harshad Surdi + Show 3 more

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https://doi.org/10.1063/1.4842615

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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 a 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.

Highlights

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
Since most of the THz emission from PCEs comes from the region very close to the anode,[7,9] it is expected that the THz emission will increase, if we can enhance carrier generation and collection near the electrode
Since the 800 nm laser pulses used for charge carrier generation penetrate only 1–2 μm into the SI-GaAs, the decrease in the electric field will not be very significant up to that depth but still it can’t be ignored whereas, in the case of patterned regions, the un-etched stripes of SI-GaAs will exhibit relatively straight field lines and with increased magnitude

Summary

Introduction

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. Improved efficiency of photoconductive THz emitters by increasing the effective contact length of electrodes

Results

Conclusion