N- and p-Type SiGe HFETs and circuits

Abstract

n- and p-Type SiGe HFETs exhibit advanced performance especially favourable for RF-applications. Due to strained channels high carrier mobilities at room temperature (2700 and 1870 cm 2/V s) and large sheet carrier densities ( n s=6.4×10 12 cm ×2 and p s=2.1×10 12 cm ×2) have been achieved. For the n-MODFET ( L G>=150 nm) tensile strained Si channels embedded in SiGe layers lead to a maximal g me of 476 mS/mm and to cut-off frequencies of f t=43 GHz and f max=92 GHz. The best results for p-type HFETs were attained for a pure Ge channel MODFET with f t=32 GHz and f max=85 GHz. Analog and digital circuit realizations for the n-MODFET resulted in a transimpedance amplifier yielding a Z 21 of 56 dB Ω at a bandwidth of 1.8 GHz and an inverter with a gate delay of 25 ps.