Ge–GaAs–Ge Heterojunction MOSFETs for Mixed-Signal Applications

Abstract

A lattice matched heterojunction intraband tunnel (HJIBT) FET is proposed. The performance dependence of the device on conduction band (CB) discontinuity at source-channel and drain-channel interface is addressed using numerical simulation. Various mechanisms governing transport phenomena in the HJIBT FET are investigated in detail for different CB offsets (CBOs). For low gate to source voltage ( ${V}_{\text {GS}}$ ), thermionic emission is found to be the most significant transport mechanism. For moderate ${V}_{\text {GS}}$ , intraband tunneling phenomenon dominates over thermionic emission and continues to remain so. At high ${V}_{\text {GS}}$ , band-to-band tunneling occurs in HJIBT FETs. The proposed device shows improved figures of merit such as drain-induced barrier lowering (DIBL), ON-current ( ${I}_{ \mathrm{\scriptscriptstyle ON}}$ ) to OFF-current ( ${I}_{ \mathrm{\scriptscriptstyle OFF}}$ ) ratio ( ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ ), subthreshold slope (SS), gate capacitance ( ${C}_{\text {G}}$ ), ${g}_{m}$ (transconductance), and ${f}_{T}$ (cut-off frequency), with respect to conventional MOSFET. Also, the design of a high-performance hybrid 6T-static random access memory (SRAM) is proposed.