Methodology to Optimize E-Mode GaN HEMT with P-Type Doping under 2DEG Layer

This article presents the methodology to optimize the enhancement-mode (E-mode) GaN high electron mobility transistor (HEMT). The focus is on the recessed Schottky gate with a p-type GaN under the two-dimensional electron gas (2DEG) layer. Design of experiment 3 factors (t<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AlGaN</inf>, L<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gate</inf>, P<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GaN</inf>) at 4 levels for technology computer-aided design (TCAD) simulation produced 2 responses (V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf>, R<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf>). 128 sets of observations are fed into the analysis of variance (ANOVA) and artificial neural network (ANN) models, where they narrowed down the list of potential optimum E-mode GaN HEMTs. The best device with t<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AlGaN</inf> = 4 nm, L<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gate</inf> = 2 µm, and P<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GaN</inf> = 1.2 ×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sup> cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">–3</sup> is predicted V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> = 1.263 V and R<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> = 3.317 Ω. The verification by TCAD gives V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> = 1.224 V and R<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> = 3.235 Ω which is very close to the ANOVA-ANN prediction. The p-type GaN under 2DEG created a local GaN p-n junction that depletes electrons in 2DEG at the thermal equilibrium.