GaN High-Electron-Mobility-Transistor on Free- Standing GaN Substrate With Low Contact Resistance and State-of-the-Art fT × LG Value

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In this article, we report on demonstrating high-performance AlGaN/GaN high-electron-mobility-transistor (HEMT) on free-standing GaN (FS-GaN) substrate with low contact resistance (RC) and high breakdown voltage (BV). Non-regrowthRCas low as0.23 Ω ·mm was achieved by using the self-aligned Ohmic etching process and nonfield plated BV as high as 193 V was also acquired due to the low dislocation density of the epi-layer on FS-GaN substrate. It is found that the reduction of theRCis induced by the smaller electron tunneling width across the AlGaN barrier layer, rather than the formation of dislocation related metal spikes. The fabricated GaN HEMT was a peak extrinsic transconductance (gₘ) of 203 mS/mm and a drain current (ID) ON/OFF ratio of 106–107. Benefited from the lowRC, a cut-off frequency/maximum oscillation frequency (fT/fₘₐₓ) of 26/73 GHz was extracted at a gate length (Lg) of 600 nm, yielding afT· Lgvalue of 15.6 GHz· μ mand a Johnson’s figure-of-merit (J-FOM) of 5.0 THz· V, which are the highest values among all AlGaN/GaN HEMTs on FS-GaN substrate. This work implies that GaN HEMTs on FS-GaN substrate with lowRCturn out to be a promising candidate for high-performance radio frequency (RF) power device applications.