Acceptor states in HgCdTe films grown by molecular-beam epitaxy on GaAs and Si substrates

A study of defects in HgCdTe films grown by molecular-beam epitaxy on GaAs and Si substrates was performed. Variable-temperature photoluminescence (PL) and carrier lifetime measurements were carried out on as-grown films and films subjected to post-growth annealings. Films grown on GaAs substrates appeared to be mostly free from defects providing energy states within the bandgap, yet specific acceptor states were generated in these films under conditions associated with mercury deficiency. The properties of films grown on Si substrates were mostly governed by two types of uncontrolled defects. Relatively deep levels with energy 40 to 70 meV were revealed with the use of PL measurements, yet their effect on the lifetime was not traced. The lifetime value was rather determined by other type of defects with energy depth of similar to 30 meV. Possible relation of these defects to the specifics of MBE growth of HgCdTe on Si substrates is discussed. (C) 2016 WILEY-VCH Verlag GmbH & Co.