Low-damage interface enhancement-mode AlN/GaN high electron mobility transistors with 41.6% PAE at 30 GHz

This paper reports a low-damage interface treatment process for AlN/GaN high electron mobility transistor (HEMT) and demonstrates the excellent power characteristics of radio-frequency (RF) enhancementmode (E-mode) AlN/GaN HEMT. An RF E-mode device with 2.9-nm-thick AlN barrier layer fabricated by remote plasma oxidation (RPO) treatment at 300 °C. The device with a gate length of 0.12-μm has a threshold voltage (V_th) of 0.5 V, a maximum saturation current of 1.16 A/mm, a high I_on/I_off ratio of 1 × 10⁸, and a 440-mS/mm peak transconductance. During continuous wave (CW) power testing, the device demonstrates that at 3.6 GHz, a power added efficiency is 61.9% and a power density is 1.38 W/mm, and at 30 GHz, a power added efficiency is 41.6% and a power density is 0.85 W/mm. Furthermore, the RPO treatment improves the mobility of RF E-mode AlN/GaN HEMT. All results show that the RPO processing method has good applicability to scaling ultrathin barrier E-mode AlN/GaN HEMT for 5G compliable frequency ranging from sub-6 GHz to Ka-band.