Copper, the dominant acceptor in refined, undoped zinc telluride

Abstract

Comparative measurements have been made of optical absorption and photoluminescence of refined undoped and Cu in-diffused ZnTe single crystals. Strong increases in a bound exciton BE line near 2.375 eV previously identified with the electrically dominant point defect acceptor ‘a’, with binding energy E A ⋍ 149 meV, suggests that this acceptor is substitutional Cu Zn. Similarly strong increases in a relatively broad band at slightly higher energy suggests the simultaneous incorporation of shallow donors, possibly interstital Cu I. These findings indicate that intrinsic defects such as V Zn neither control the Fermi level in refined ZnTe nor produce shallow acceptors with E A ≲ 250 meV, contrary to much previous speculation.