Patent ID: 7723667

Claim:
A phototransistor, comprising: a photo-sensitive semiconductor layer; a barrier layer extending across an active region of the semiconductor layer; a drain region laterally spaced from the active region of the semiconductor layer; a drain contact connected to the drain region; a source layer on the other side of the barrier layer to the semiconductor layer; a gate layer on the opposite side of the semiconductor layer to the barrier layer and laterally overlapping the barrier layer for controlling the barrier height of the barrier layer to control conduction of electrons and holes between the source layer and the active region; and a gate insulator layer between the gate layer and the semiconductor layer; wherein the phototransistor allows light incident on the phototransistor to reach the active region to create electron hole pairs in the active region, the holes accumulating at the barrier to change the effective barrier height and hence the current flow between source layer and drain region through the active region.