Origin of recombination transitions at the lattice-matched GaInAsSb-GaSb n-N type-II heterojunctions

Luminescence properties of GaSb-GaInAsSb isotype type-II heterojunctions with various dopings have been investigated. GaInAsSb n-type epitaxial layers were grown by liquid-phase epitaxy on Czochralski-grown N-type substrates with different tellurium concentrations. Two main luminescent peaks with mutual interchange of intensity and with wavelength shift were observed, both with temperature and excitation intensity. This effect is dependent on dopant concentration in the substrate, as well as in the layer. The explanation of this effect is based on the dominant role of double acceptor levels as final states for the luminescent transitions. A new band in the luminescence spectra was found which is interpreted as a tunneling recombination of the conduction electrons with the photoexcited holes trapped on native acceptors in the band-bending region at the GaSb side of the heterojunction.