P-type wurtzite GaN/AlGaN quantum well structures for normal incidence inter-subband photodetectors at 1.55 μm

The inter-subband (ISB) absorption of wurtzite (WZ) p-type GaN/AlGaN quantum well (QW) structures was theoretically investigated as a function of Al content in the barrier by using the multiband effective mass theory. The GaN/AlGaN QW structure with x = 0.7 shows the peak wavelength of the TE-polarized absorption spectrum at 1.55 μm. The peak intensity of the TE-polarized absorption spectrum is much higher than that of the TM-polarized absorption spectrum. We expect that a p-type WZ GaN/AlGaN heterostructure with a relatively low Al content (x = 0.7) will be attractive for a normal incidence photodetector application for fiber-optic communications because the free hole concentration of about 1 × 10¹⁷ cm^-3 is expected to be possible on the experimental side.