Electronic properties of the Au impurity in Hg0.75Cd0.25TeHg0.75Cd0.25Te: First-principles study

The structural and electronic properties of the gold in situ impurity (AuHgAuHg) and gold interstitial defect (AuiAui) in Hg0.75Cd0.25TeHg0.75Cd0.25Te (MCT) have been studied by plane-wave pseudopotential methods based on the density functional theory. Valence charge density, electron localization function (ELF), density of states and formation energy of gold impurity and defect were calculated to reveal the dopant stability and doping efficiency. The results indicate that the in situ gold impurity maintains a relative strong bonding with the host atom. The impurity AuHgAuHg creates a shallow acceptor level that is 23 meV above VBM. However, the interstitial gold defect is dominant donor. Under Hg-rich molecular beam epitaxy (MBE) growth condition, due to the self-compensating effect between AuHgAuHg and AuiAui, the Fermi level is pinned close to CBM by which the gold impurity cannot behave as an efficient acceptor. Whereas under Te-rich MBE growth condition and liquid phase epitaxy (LPE) growth condition, the self-compensating effect is overcame and the in situ gold impurity acts as an efficient p-type dopant.