Title Enhanced sensitivity AlGaN/GaN HEMT terahertz detector without ungated regions /
Authors Vyšniauskas, Juozas ; Ikamas, Kęstutis ; Lisauskas, Alvydas
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Is Part of 17th International conference on Advanced properties and processes in optoelectronics materials and systems (Apropos 17) : September 30 - October 1, 2020, Vilnius, Lithuania : book of abstracts.. Vilnius. 2020, p. 22
Keywords [eng] detector ; HEMT ; THz ; AlGaN/GaN ; sensitivity ; transistor
Abstract [eng] AlGaN/GaN HEMTs [1,2] and nMOS [3] transistors are reported as the most sensitive field effect transistor-based terahertz detectors. The advantage of HEMT is high electron mobility (up to 1500 cm2 /Vs) and the disadvantage is the presence of passive ungated regions which introduce additional series impedance contributing to the loss of high-frequency signal. The advantage of nMOS is the absence of ungated regions and the disadvantage is low electron mobility (about 250 cm2/Vs) due to high acceptor density (about 2e18 cm-3) in the channel. Here, we propose the HEMT-based THz detector with 5 nm HfO2 dielectric between the gate electrode and the AlGaN layer, which allows to separate the gate from the source and drain terminals without involving ungated regions. For numerical calculations of detector characteristics, we have employed two-dimensional hydrodynamic modeling performed with Synopsys TCAD Sentaurus program package comprising Poisson's equation, continuity equation, current density equation and energy balance equation for electrons and holes. It accounts for the formation of spontaneous and piezoelectric polarization charges in GaN and AlGaN layers, as well as the dependence of carrier mobility on doping density and carrier temperature. The comparison of current responsivity of the HEMT with and without ungated regions and the gate length LG = 100 nm is shown in Fig. 1. The results clearly indicate that the presence of ungated regions with the length LUG = 100 nm reduces the maximum of the current responsivity at 1 THz by about 2 times. The minimum NEP at 1 THz is about 3 times lower in the HEMT without ungated regions.
Published Vilnius
Type Conference paper
Language English
Publication date 2020