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 SiO 2 mask by significantly increasing the thickness of the SiO 2 mask to surpass that of the growing GaAsSb layer. We successfully fabricated p-GaAsSb/i-InGaAs tunnel FETs using a thick SiO 2 mask, wherein the carrier concentration of the p-GaAsSb source was 5 × 10 19 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 × 10 4 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 d Ψ s / d ( log 10 I D ) is estimated as 52 mV dec −1 .