MBE AlxGa1-xAs/GaAs phototransistors sensitive at low illumination

Floating base Al
0.4
Ga
0.6
As heterojunction bipolar transistors have been grown with MBE with optical gains near unity at illumination levels down to < 10 pW for a 5 × 10
^-4
cm
²
device area. Dark currents are below 1 pA for the best devices. A maximum gain of 8 to 10 is observed at ∼ 1 W/cm
²
incident power level.