CONSEQUENCES OF SUBBAND NONPARABOLICITY ON INTERSUBBAND EXCITATIONS IN P-DOPED GAAS ALXGA1-XAS QUANTUM-WELLS/

By means of resonance Raman spectroscopy we have observed a characteri stic shift of hole-intersubband transitions with excitation energy in p-doped GaAs/AlxGa1-xAs quantum-well structures. As possible reasons f or the shift, the nonparabolicity of the valence subbands as well as f luctuations of the well width are discussed. Both contributions can be separated experimentally by application of an external magnetic field , which quantizes the in-plane motion of the carriers. For our samples , we can show that the shifts observed for B = 0 T are mainly caused b y subband nonparabolicity. This interpretation is confirmed by a compa rison with results of a simulation of single-particle Raman spectra ba sed on a subband calculation with Luttinger's 4 x 4 Hamiltonian. Corre sponding shifts are observed both in depolarized and polarized spectra .