Excitons at the p-type modulation doped Al0.5Ga0.5As/GaAs interface

Two dimensional hole gas (2DHG) created at modulated doped Al 1- x Ga x As/GaAs heterostructures was studied by optical methods. Samples of different 2DHG concentration p=9.8*10 11 cm $min2 were examined by means of photo luminescence (PL) and photo luminescence excitation (PLE) measurements under magnetic field up to 8T in Faraday configuration. In PL spectra two groups of lines are observed: a broad line at lower energy so called H-band and at higher energy exciton related lines. In magnetic field H-band splits and shifts linearly following Landau level quantization whereas higher energy lines exhibit diamagnetic shift. A strong absorption of H-band in PLE spectra is observed. We propose consistent theoretical model which explains both the nature of H-band and the formation of excitons on 2DHG states.