AN IMPROVED THEORETICAL-MODEL TO EXPLAIN ELECTRONIC AND OPTICAL-PROPERTIES OF P-TYPE CAAS ALGAAS SUPERLATTICES FOR MULTIWAVELENGTH NORMAL INCIDENCE PHOTODETECTORS/

We extend our previous theoretical analysis of electronic and optical properties of p-type quantum well structures based on the two heavy- a nd light-hole system to include all the three valence bands. These the ories are then used to clarify the origin of the normal incidence abso rption and photocurrent at photon wavelengths of 2 - 3 mu m, which was observed in addition to the absorption around 8 mu m by a recent expe rimental investigation with heavily doped p-type GaAs/AlGaAs multi-qua ntum well (MQW) structures. In the theoretical analysis, the Hartree a nd exchange-correlation many-body interactions are taken into account within one-particle local density approximation, and it is shown that normal incidence absorption occurs in two wavelength regions over the transition energy range higher than barrier height for p-type GaAs/AlG aAs superlattices with well doping of 2 x 10(19) cm(-3); one region ha s broad absorption peaks with coefficients of about 5000 cm(-1) around 8 mu m, and the other has two rather sharp peaks at 2.7 mu m and 3.4 mu m with 1800 cm(-1) and 1300 cm(-1), respectively. The result indica tes that the theory explains the experimental observation well, as the theoretical and experimental results are in close agreement in genera l absorption features.