Comprehensive Characterization and Modeling of the Abnormal Gate Leakage Current in Pseudomorphic HEMTs

Abstract

Systematic characterization and qualitative modeling of the abnormal gate leakage current in GaAs-based commercial pseudomorphic HEMTs with gate lengths of 0.2 μm are reported with a unique resonant tunneling mechanism for the first time. In the modeling of the abnormal IV characteristics, all possible physical mechanisms are included for a proper description and the characteristics are divided into 4 different voltage regions. They consist of the normal reverse leakage current, the negative hump due to impact ionization, the abnormal positive hump induced by the resonant tunneling, and the forward conduction that results in a negative differential resistance (NDR) for the drain current. In particular, the abnormal positive and negative humps in the gate current and the negative differential resistance (NDR) in the drain current have been investigated, and physical models are provided. Experimental verification has been also provided for the abnormal gate leakage current that occurs under a high drain bias (VDS>2.3 V) with a forward gate bias (0.2<VGS<0.6) due to the formation of hybrid-excited states across the InGaAs channel and the AlGaAs donor layer. These results will provide a comprehensive interpretations of the abnormal positive humps in IG caused by resonant-tunneling and of the NDR of the drain current due to a field-assisted tunneling real-space transfer caused by hot channel electrons. This work is also expected to be helpful for implementing more robust and reliable pseudomorphic HEMT-based MMICs and MIMICs.