Electronic and intersubband optical properties of p-type GaAs/AlGaAs superlattices for infrared photodetectors

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Abstract
Existing theories of electronic properties and optical transitions in quantum‐well structures are extended to p‐type superlattices including the two heavy‐ and light‐hole valence bands. These theories are then used to elucidate the normal incidence optical‐absorption mechanisms including the Hartree and exchange‐correlation many‐body interactions on the basis of the one‐particle local density approximation. The effects of doping density and doping configuration on the electronic structure and the intersubband optical properties of heavily doped p‐type GaAs/AlGaAs superlattices are investigated for use in infrared photodetectors. It is shown that these many‐body interactions cause significant changes to the subband energy structure and the optical‐absorption coefficient, and that the doping level and doping configuration have an important effect on the properties of these superlattices. Peak absorption coefficients of 6000–10 000 cm−1 for normal light incidence at photon wavelengths of 8–10 μm are predicted for p‐type GaAs/AlGaAs superlattices with well doping of 2×1019 cm−3. Because of the heavier effective mass of holes in the p‐type structures, as compared to the n‐type structures, a relatively slower degradation of the dark current with increasing doping density is expected. This, in addition to the higher absorption values that can be achieved with heavily doped p‐type superlattices, renders them highly promising for normal incidence photodetectors.