High RF Performance AlGaN/GaN HEMTs on 6-in Si Substrate for Low Voltage Applications

In this letter, AlGaN/GaN high electron mobility transistors (HEMTs) on a 6-inch Si substrate with excellent RF performance are presented for low voltage applications. Using regrown n+-InGaN ohmic contacts by metal-organic chemical vapor deposition, the ohmic contact resistance achieves an average value of $0.08~\Omega \cdot $ mm on the whole wafer. With a gate length of 220 nm and a source-drain spacing of $2.2~\mu $ m, the device exhibits a saturation current of up to 1689 mA/mm and a peak transconductance of 436 mS/mm. Once the wafer was thinned to $100~\mu $ m, 3.6 GHz load-pull measurements for the HEMT with gate width ( ${W}_{\text {g}}\text {)}$ of $2\times 100~\mu $ m at low drain voltages ( ${V}_{\text {d}}\text {)}$ of 5-15 V indicate that the device exhibits maximum output power densities ( ${P}_{ {\text {out}, {max}}} )$ of 0.86-4.35 W/mm and peak power added efficiencies (PAE) of 63.96%-66.23%, which are the highest output power density and PAE from AlGaN/GaN HEMTs at the same operating voltage level in sub-6GHz. Furthermore, the HEMT with ${W}_{\text {g}}$ of $8\times 125~\mu $ m also shows high PAE of 60.4%/61.19% and ${P}_{ {\text {out}, {max}}}$ of 0.56/0.75 W/mm at ${V}_{\text {d}} =5$ /6 V. The excellent properties of these AlGaN/GaN HEMTs on Si illustrate their suitability for addressing specific RF application scenarios, including portable communication devices, wireless sensor networks and so on.