NOVEL GAAS/ALGAAS MULTIQUANTUM-WELL SCHOTTKY-JUNCTION DEVICE AND ITS PHOTOVOLTAIC LWIR DETECTION

We have, for the first time, demonstrated photovoltaic detection for a multiple quantum-well (MQW) long-wavelength infrared (LWIR) detector. With a blocking layer, the MQW detector exhibits Schottky I-V characteristics with extremely low dark current and excellent ideality factor. The dark current is 5 x 10(-14) A for a 100 x 100-mu-m2 detector (designed for 10-mu-m response) at 40 K, nearly nine orders of magnitude lower than that of a similar MQW LWIR detector without the blocking layer. The ideality factor is approximately 1.01-1.05 at T = 40-80 K. The measured "Schottky"-barrier height is consistent with the energy difference between first excited states and ground states, or the peak of spectral response. We also, for the first time, report a measured effective Richardson constant (A**) for a GaAs/AlGaAs heterojunction using this blocking layer structure. The A** is low approximately 2.3 A/cm2/K2.