AlGaN/GaN High-Electron-Mobility Transistors on a Silicon Substrate under Uniaxial Tensile Strain

This paper reports pulsed DC and RF characteristics of GaN high-electron-mobility transistors (HEMTs) on a silicon substrate under external mechanical tensile strain. Tensile strain enhanced two-dimensional electron gas (2DEG) density resulted in increasing I_D, f _T and f _max at CW measurement. Eliminating self-heating by pulse measurement, DC and RF characteristics between flat and bend devices were slightly increased for small-width devices, and decreased for wide-width devices. This was because maximum electron drift velocity was reduced by a hot phonon effect while 2DEG density increased by tensile strain for wide-width devices. Results indicated that the tensile strain on thinner substrates decreased the DC and RF performances of wide-width GaN-based RF power devices. This phenomenon should be considered while using GaN-based RF power devices for compact packages, especially in high-power applications.