Full-Wafer Characterization of AlGaN/GaN HEMTs on Free-Standing CVD Diamond Substrates

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We report on electrical characterization and uniformity measurements of the first conventionally processed AlGaN/GaN high electron mobility transistors (HEMTs) on free-standing chemical-vapor-deposited (CVD) diamond substrate wafers. DC and RF device performance is reported on HEMTs fabricated on <formula formulatype="inline"><tex Notation="TeX"> $\sim\!\!\hbox{130-}\mu\hbox{m}$</tex></formula>-thick and 30-mm round CVD diamond substrates without mechanical carrying wafers. A measured <formula formulatype="inline"><tex Notation="TeX">$f_{T} \cdot L_{G}$</tex></formula> product of 12.5 <formula formulatype="inline"><tex Notation="TeX">$\hbox{GHz} \cdot \mu\hbox{m}$</tex></formula> is the best reported data for all GaN-on-diamond technology. X-band power performance of AlGaN/GaN HEMTs on diamond is reported to be 2.08 W/mm and 44.1% power added efficiency. This letter demonstrates the potential for GaN HEMTs to be fabricated on CVD diamond substrates utilizing contact lithography process techniques. Further optimization of the epitaxy and diamond substrate attachment process could provide for improvements in thermal spreading while preserving the electrical properties. </para>