MBE and MOCVD growth of AlGaAsAlAsGaAs double barrier multiple quantum well infrared detector

We have studied both the molecular-beam epitaxy (MBE) and metal-organic chemical vapour deposition (MOCVD) grown AlGaAsAlAsGaAs double barrier multiple quantum well structures for 3–5 μm infrared (IR) photodetector application. The intersubband absorptions of these samples were measured at the Brewster angle as well as through a multipass 45° wedge waveguide. In the former case, we have also studied the polarisation dependence of the IR transmission. The MBE grown sample has an absorption at about 3.1 μm, while the absorption peak for the MOCVD sample is shifted slightly, depending on the wafer location. The low temperature photoluminescence peaks show a significant shift when the probe position is moved across the MOCVD wafer along the gas flow direction, owing to thickness non-uniformity. This variation was also confirmed by double crystal X-ray diffraction data. Theoretically, we have carried out a bound and quasibound state energy calculation for these structures as a function of well width and related them to the experimental results. In addition, the IR photoresponse for the MBE grown sample at about 80 K has been measured for IR photodetector application.