Geometric effects in the Dyakonov-Shur theory of Teraherz photodetection

TL;DR

This paper extends the Dyakonov-Shur theory of Terahertz photodetection to account for short gates and multiple gates in field-effect transistors, revealing how gate positioning affects detection efficiency.

Contribution

It provides a comprehensive theory for THz photodetection with short and multiple gates, including an analytical formula for optimal gate placement.

Findings

Short gate positioning reduces detection efficiency.

Optimal gate placement can be estimated analytically.

Multiple gates influence the plasma wave resonance behavior.

Abstract

Nonlinear resonances of plasma waves in field-effect transitors enable a well-known photodetection mechanism, first introduced by Dyakonov and Shur in the Nineties, especially suited to the Terahertz (THz) frequency range. Theoretical analyses of the mechanism always assume that the gate of the transistor, which is coupled to the antenna receiving the THz signal, is as long as the channel itself, at odds with typical experimental devices, where short gates are usually employed, e.g. due to fabrication constraints. In this work we overcome this limitation and provide a complete theory of Dyakonov--Shur photodetection in the presence of short gates. We develop our theory in such a general fashion that allows us to also treat the case in which multiple gates are present. We find that a sub-optimal positioning of the gates can substantially decrease the detection efficiency of the device and provide a compact analytical formula to quickly estimate the optimal gate position.