A Temperature Stable Amplifier Characteristics of AlGaN/GaN HEMTs on 3C-SiC/Si
Arijit Bose, Debaleen Biswas, Shigeomi Hishiki, Sumito Ouchi, Koichi Kitahara, Keisuke Kawamura, Akio Wakejima
Abstract
A high temperature stable amplifier characteristics for L-band or 2 GHz was studied using AlGaN/GaN high electron mobility transistors (HEMTs) on 3C-SiC/Si substrate. A crack free, high quality AlGaN/GaN heterostructure on a 6-inch Czochralski (Cz)-Si substrate was realized by metal oxide chemical vapor deposition (MOCVD). The epitaxial structure comprises an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8~\mu \text{m}$ </tex-math></inline-formula> thick nitride layer and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1~\mu \text{m}$ </tex-math></inline-formula> thick 3C-SiC intermediate layer. The fabricated AlGaN/GaN HEMT achieved excellent electron transport characteristics along with a comparable cutoff frequency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}~_{\text {T}}$ </tex-math></inline-formula> ) of 4.8 GHz for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2~\mu \text{m}$ </tex-math></inline-formula> gate length device. Temperature dependent S-parameter measurement of open pad structures achieved outstanding temperature stability up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$125~^\circ \text{C}$ </tex-math></inline-formula> . Continuous wave power measurements showed a 2 GHz continuous wave power density of 2 W/mm, a maximum power added efficiency (PAE) of 47% along with a linear gain of 17.2 dB for class A amplifier operation. Moreover, at elevated temperature of up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$125~^\circ \text{C}$ </tex-math></inline-formula> , the minimal power performance degradation was mainly attributed to the intrinsic property of the device, thus elimination of RF leakage from the buffer or epitaxial layers at high temperatures was confirmed.