Far-infrared spectra of reflectivity, transmission and hot-hole emission in p-doped GaAs/Al_0.5Ga_0.5As multiple quantum wells

Far-infrared reflectivity and transmission spectra have been measured for p-doped GaAs/Al_0.5Ga_0.5As multiple quantum wells (MQWs) using polarized oblique-incidence Fourier transform spectroscopy (FTS). Theoretical calculations have been performed within a bulk slab effective-medium scheme, modified to include an anisotropic plasma response in the wells, and successfully compared with the experimental data. The optics of the observed features are discussed, with particular reference to interference modes. Far-infrared intersubband absorption at 80 cm^-1 was observed by Brewster's angle (θ = 73°) transmission measurements. Furthermore, we present the first observation of far-infrared emission by two-dimensional hot holes in MQWs due to heating of holes by a longitudinal electric field applied along the layers. The observed emission energies are attributed to direct transition of hot holes between subbands of the valence band due to size quantization.