Mixing of impurity levels by a built-in electric field in a CdMgTe/CdZnTe heterostructure

Magneto-optical studies were performed on a Cd_0.88Mg_0.12Te/Cd_0.97Zn_0.03Te heterostructure in which the CdMgTe barrier was δ-doped with iodine donors and the CdZnTe channel was δ-doped with nitrogen acceptors. The photoluminescence spectrum was dominated by a line with an energy close to that of the CdMgTe barrier which is interpreted as a result of donor–acceptor transitions. Stokes parameters polarisation spectroscopy showed that the line was purely circularly but very weakly polarised (8% in 6 T). It was proposed that this weak degree of polarisation comes from mixing of impurity levels by a strong electric field present in the investigated structure.