A Temperature Stable Amplifier Characteristics of AlGaN/GaN HEMTs on 3C-SiC/Si

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> <tex-math notation= LaTeX >$8~\\mu \\text{m}$ </tex-math></inline-formula> thick nitride layer and a <inline-formula> <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> <tex-math notation= LaTeX >${f}~_{\\text {T}}$ </tex-math></inline-formula>) of 4.8 GHz for <inline-formula> <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> <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> <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.