E-Mode AlN/GaN HEMTs on Si With 80.4% PAE at 3.6 GHz for Low-Supply-Voltage RF Power Applications

Enhancement-mode (E-mode) AlN/GaN high electron mobility transistors (HEMTs) with a 160-nm T- shape recessed gate on a silicon substrate were fabricated. The fabricated device has a ${V}_{\text {TH}}$ of +0.35 V, and shows a maximum drain current ( ${I}_{\text {DMAX}}\text {)}$ of 1.58 A/mm, a low on- resistance ( ${R}_{\text {ON}}\text {)}$ of $1.8~\Omega \cdot $ mm, and a peak transconductance ( ${G}_{\text {MMAX}}\text {)}$ over 580 mS/mm. A cut-off frequency ( ${f}_{\text {T}}\text {)}$ of 85 GHz and a maximum oscillation frequency ( ${f}_{\max }\text {)}$ of 75 GHz were obtained. Load pull continuous-wave (CW) power sweep measurement at 3.6 GHz demonstrated a peak power-added-efficiency (PAE) of 71.4% and a saturated output power density ( ${P}_{\text {out}}\text {)}$ of 0.70 W/mm at ${V}_{\text {DS}}=6$ V. At 3.6 GHz pulsed wave (PW) power sweep at ${V}_{\text {DS}}=6$ V the device demonstrated an 80.4% PAE and 0.5 W/mm associated ${P}_{\text {out}}$ . These results promises the great potential of E-mode AlN/GaN HEMTs with gate recess in the applications of low supply voltage RF power applications.