GaAsSb/InGaAs tunnel FETs using thick SiO2 mask for regrowth

Abstract

The regrowth conditions for lateral tunnel FETs featuring heterojunctions involve a tradeoff between selective growth and heavy doping. This study mitigated the connection between single crystals on the InP layer and polycrystals on the SiO2 mask by significantly increasing the thickness of the SiO2 mask to surpass that of the growing GaAsSb layer. We successfully fabricated p-GaAsSb/i-InGaAs tunnel FETs using a thick SiO2 mask, wherein the carrier concentration of the p-GaAsSb source was 5 × 1019 cm−3, and the growth temperature was maintained at 500 °C. The observed current–voltage (I–V) characteristics exhibited an on/off ratio of 5 × 104 and demonstrated ambipolar current behavior, confirming the presence of a p-type source. However, the observed subthreshold swing (SS) was limited to 120 mV dec−1. In comparison with the I–V characteristics of the planar transistor, degradation of SS can be explained by interface state, and the factor that characterizes the change of the drain current with the surface potential dΨs/d(log10ID) is estimated as 52 mV dec−1.