Effect of doped substrate on GaAs-AlGaAs interfacial workfunction IR detector response through cavity effect

In this paper, results are reported showing response enhancement in GaAs-AlGaAs IR detectors using a doped substrate to increase reflection, enhancing the resonant cavity effect. Responsivity for heterojunction interfacial workfunction detectors grown on semi-insulating (SI) and doped substrates are compared. For a device grown on an SI substrate, a 9-μm resonance peak had a response of 1.5 mA/W while a similar device on an n-doped substrate showed 12 mA/W. Also, the difference between response under forward and reverse bias (3 versus 12 mA/W) for the sample grown on the doped substrate, as well as calculated results confirm that the increased response is due to the resonant enhancement. An optimized design for a 15-μm peak (24 μm 0 response threshold) detector grown on a doped substrate could expect a peak response of 4 A/W with a 50% quantum efficiency and D^* ∼ 2 × 10¹⁰ Jones at the background limited temperature of 50 K.