Interband optical absorption in free standing layer of Ga0.96In0.04As0.99N0.01

We have measured the interband optical absorption of a free-standing sample of Ga0.96In0.04As0.99N0.01 in a wide energy range from 1 to 2.5 eV. We fou nd that the fundamental absorption edge is shifted by 150 meV towards lower energies, and the absorption coefficient measured at higher energies exhib its substantial reduction comparing to that of GaAs. By removing the GaAs s ubstrate, we were able to get an experimental insight into the interband op tical transitions and the density of state in this material. The changes ca n be understood within the band anticrossing model predicting the conductio n band splitting. New absorption edges associated with optical transitions from the spin-orbit split off band to the lower conduction subband (1.55 eV ) and from the top of the valence band to the upper subband (1.85 eV) are o bserved. (C) 2000 American Institute of Physics. [S0003-6951(00)03210-1].