Characterization of Subgap Density-of-States by Sub-Bandgap Optical Charge Pumping in In_0.53Ga_0.47As Metal-Oxide-Semiconductor Field-Effect Transistors

We report an experimental characterization of the interface states (D _it(E)) by using the subthreshold drain current with optical charge pumping effect in In_0.53Ga_0.47As metal-oxide-semiconductor fieldeffect transistors (MOSFETs). The interface states are derived from the difference between the dark and photo states of the current–voltage characteristics. We used a sub-bandgap photon (i.e., with the photon energy lower than the bandgap energy, E _ph < E _g) to optically excite trapped carriers over the bandgap in In_0.53Ga_0.47As MOSFETs. We combined a gate bias-dependent capacitance model to determine the channel length-independent oxide capacitance. Then, we estimated the channel length-independent interface states in In_0.53Ga_0.47As MOSFETs having different channel lengths (L _ch = 5, 10, and 25 [μm]) for a fixed overlap length (L _ov = 5 [μm]).