Effects of valence-band mixing on the Franz-Keldysh spectra in quantum well

Using 4 × 4 Luttinger Hamiltonian, we compute the opto-absorption spectra for a 200 Å quantum well. The mixing between heavy-hole and light-hole renders non-parabolic valence subbands, therefore deforms the stair-like spectra. The electric field modulation spectra exhibit oscillatory feature, but the oscillations is different in nature from the bulk Franz-Keldysh oscillation. Stark shift of confine levels brings about the oscillations. Imposing a 10 meV broadening, it is impractical to determine the confine energies from the modulation spectra. Instead, we find that the polarization-modulation spectra contain more clear information about the confine levels.