Photoluminescence study of impurity states in aluminum antimonide

We have characterized Czochralski-grown undoped AlSb single crystals by low-temperature photoluminescence and photoluminescence excitation spectroscopy. An excitonic band-gap energy Egx =1.667±0.001 eV of AlSb was determined. In all samples we detect a dominant donor and acceptor. The donor binding energy ED =151±3 meV and acceptor binding energy EA =37±3 meV are deduced from donor-acceptor pair luminescence and the excited states of the acceptor from selective pair excitation. We tentatively identify the donor as sulfur and the acceptor as carbon.