Formation of deep complexes in ZnSe during ohmic contact annealing

Abstract
The formation of ohmic contacts to n-ZnSe grown by metalorganic vapor-phase epitaxy (MOVPE) on GaAs was investigated by current-voltage and photoluminescence (PL) measurements. Annealing of the contacts even at temperatures as low as 300 °C causes the formation of deep complexes with PL emissions at 2.25–2.35 and 1.97 eV. These centers degrade the electrical and optical properties of the ZnSe epitaxial layers. The effects of strain and Ga outdiffusion on ohmic contact properties was investigated in ZnSe layers of various thicknesses. Due to a gallium-doped ZnSe transition layer at the substrate heterointerface ohmic contacts are easily formed only on thin layers.