Terahertz detection by AlGaN/GaN HEMTs at high intensity

We report on the photoresponse of AlGaN/GaN HEMT to THz radiation of low and high intensity. We show that the response vs. gate bias dependence can be described by the theory of Dyakonov-Shur in the whole range of radiation intensity. Unusual behavior of the photoresponse vs. intensity was observed under laser irradiation: a quadratic increase of the response followed by saturation. We speculate that this phenomenon can be explained by hot electrons capture by traps in AlGaN or buffer layers.

I. Introduction

The origins of non-linearity and saturation of responsivity of Field Effect Transistors (FETs) [1] at high intensity terahertz (THz) radiation are still not well understood.