Acceptor doping in ZnSe versus ZnTe

It is a long-standing puzzle that ZnSe is difficult to dope p type, while ZnTe - which is very similar to ZnSe - is very easily doped p type. We report ab initio calculations which show that the solubilities of Li and Na acceptors are much greater in ZnTe than the solubilities of the same acceptors in ZnSe. We trace the origin of this difference to the bonding properties of the acceptors with the neighboring chalcogens. Our results also explain the experimentally observed dependence on dopant concentration of the dislocation density in p-type ZnSe epilayers grown on GaAs.