A calculation on intersubband optical transitions including heavy and light hole bands to spin-split-off band in heavily dopedp-type GaAs/AlGaAs multi-quantum well (MQW) structures is reported. The analysis is focused on elucidating the recent experimental observation of normal incidence absorption and photocurrent at photon wavelengths of 2–3 &mgr;m, in addition to the already-observed absorption at around 8 &mgr;m in heavily dopedp-type GaAs/AlGaAs MQW structures. The calculation is an extension of our previous study which only includes transitions between heavy and light bands. The analysis, in which Hartree and exchange-correlation many-body interactions are taken into account within one-particle local density approximation, shows that normal incidence absorption occurs in two wavelength regions over the transition energy range higher than the barrier height forp-type GaAs/AlGaAs superlattices with well doping of 2×1019cm−3. One region has broad absorption peaks with coefficients of about 5000 cm−1at around 8 &mgr;m, and the other has two rather sharp peaks at 2.7 and 3.4 &mgr;m with 1800 and 1300 cm−1, respectively. The result agrees reasonable well with the experimental observation in general absorption features. The existence of multiabsorption wavelengths in heavily doped GaAs/AlGaAs MQWs may allow the design of multicolor normal incidence photodetectors. ©1997 American Institute of Physics.