Effect of Gate Length on Device Performances of AlSb/InAs High Electron Mobility Transistors Fabricated Using BCl3 Dry Etching

In this paper, we present the development of a mesa isolation process for AlSb/InAs high electron mobility transistors (HEMTs) using inductively coupled plasma (ICP) etching with BCl 3 gas. Devices with different gate lengths ($L_{\text{g}}$: 60, 100, and 200 nm) fabricated by this dry etching technique show good DC and RF performances. With an appropriate $L_{\text{g}}$/gate-channel distance ratio, the 200-nm-gate has very high peak transconductances of 781 mS/mm at $V_{\text{DS}} = 0.1$ V and 2000 mS/mm at $V_{\text{DS}} = 0.5$ V. Moreover, an extrinsic current gain cutoff frequency of 137 GHz and maximum oscillation frequency of 97 GHz were achieved at a drain bias voltage $V_{\text{DS}} = 0.3$ V, indicating the great potential for such a device operating at high frequency with extremely low DC power consumption.