Hole-intersubband excitations and luminescence transitions in p-doped GaAs---AlGaAs multiple quantum wells

Abstract

We have performed resonant Raman spectroscopy on two p-type modulation-doped GaAs---AlGaAs multiple quantum well structures with well widths dW = 10 nm and dW = 30 nm. With the frequency of the dyelaser nearly in resonance with the energy difference between conduction and valence band states of the same subband quantum number n we simultaneously observe Raman intensity of hole intersubband transitions to primarily heavy hole subbands hn and luminescence from the excited conduction subbands cn. In both samples one of the intersubband transitions is coupling to the quantum well LO-phonon. Beside these interacting excitations a second quantum well, non-coupling LO-phonon mode exists, which in our opinion is of shorter wavelength type than the coupling one. The comparison of the maxima of its scattering cross section with the resonances of the hole-intersubband transitions yields information about the intermediate states of the scattering process and confirms calculations of Zhu et al. [ 7 ], which are performed for a sample with a well width of 10.2 nm.