High performance 0.1 μm gate-length p-type SiGe MODFET's and MOS-MODFET's

Abstract

High performance p-type modulation-doped field-effect transistors (MODFET's) and metal-oxide semiconductor MODFET (MOS-MODFET) with 0.1 μm gate-length have been fabricated on a high hole mobility SiGe/Si heterojunction grown by ultrahigh vacuum chemical vapor deposition. The MODFET devices exhibited an extrinsic transconductance (g m) of 142 mS/mm, a unity current gain cut-off frequency (f T) of 45 GHz and a maximum oscillation frequency (f MAX) of 81 GHz. 5 nm-thick high quality jet-vapor-deposited (JVD) SiO 2 was utilized as gate dielectric for the MOS-MODFET's. The devices exhibited a lower gate leakage current (1 nA/μm at V gs = 6 V) and a wider gate operating voltage swing in comparison to the MODFET's. However, due to the larger gate-to-channel distance and the existence of a parasitic surface channel, MOS-MODFET's demonstrated a smaller peak g m of 90 mS/mm, f T of 38 GHz, and f MAX of 64 GHz. The threshold voltage shifted from 0.45 V for MODFET's to 1.33 V for MOS-MODFET's. A minimum noise figure (NF min) of 1.29 dB and an associated power gain (G a) of 12.8 dB were measured at 2 GHz for MODFET's, while the MOS-MODFET's exhibited a NF min of 0.92 dB and a G a of 12 dB at 2 GHz. These dc, rf, and high frequency noise characteristics make SiGe/Si MODFET's and MOS-MODFET's excellent candidates for wireless communications.