A high sensitivity, high bandwidth In/sub 0.53/Ga/sub 0.47/As/InP heterojunction phototransistor

The effects of inserting a thin, low-doped InP layer into the emitter of an N-InP/p/sup +/-In/sub 0.53/Ga/sub 0.47/ As/n-In/sub 0.53/Ga/sub 0.47/As heterojunction phototransistor were investigated by both numerical simulation and experiments. This high-low emitter structure can improve both sensitivity and bandwidth over conventional structures at low input optical power by decreasing the bulk recombination current at the heterointerface. Experimental results show that the photocurrent gain is independent of the incident power at high input powers. At low input power, the gain is found to have a small power dependence, with an ideality factor of 1.25. A current gain as high as 260 is obtained at an input power of only 40 nW.<>