Ka band High RF performance AlGaN/GaN HEMTs

To realize high RF performance AlGaN/GaN high electron mobility transistor (HEMT), two SiNx passivation layers were respectively grown on the surface of AlGaN/GaN epi wafer by inductively coupled-plasma chemical vapor deposition (ICP-CVD) and plasma enhanced chemical vapor deposition (PECVD). The two-stage passivation can effectively suppress the current collapse and decrease the parasitic parameters. To verify the performance improvement, a 6 × 50 μm GaN HEMT device was fabricated and measured. The device shows a maximum drain current of about 1067 mA/mm and a maximum transconductance of about 433 mS/mm, the cut-off frequency (fT) of 45.4 GHz at a gate bias of -1.5 V and a drain bias of 20 V. The device shows a power density of 3.7 W/mm, a power-added efficiency (PAE) of 46.5% and power gain of 8.5 dB by load-pull measurement. In addition, a 34-36 GHz GaN monolithic microwave integrated circuit (MMIC) was fabricated, which exhibits an output power of about 41.5 dBm, a PAE of 20% and a gain of 15.5 dB.