MBE grown BeTe and ZnBeTe films as a new p-contact layer of ZnSe-based II–VI lasers

Abstract

Non-alloyed Au/p-ZnSe/p-BeTe ohmic contact layers for ZnSe-based blue–green laser diodes with contact resistivity as low as 4.2×10 −4 Ω cm 2 are reported. This contact layer is basically dislocation free due to small lattice misfit as long as the thickness is thinner than 500 Å, as confirmed by transmission electron microscopy (TEM) observation. The ZnSe layer serves as a contact layer for BeTe and protecting layer against oxidation as well. The electrical properties of the contact layers are strongly dependent on the ZnSe layer thickness. Au diffusion through the ZnSe layer down to the BeTe layer at room temperature is found to be responsible for ohmic properties. A series of ZnBeTe epilayers with different x values have been grown on GaAs by molecular beam epitaxy (MBE). We can easily control the composition by changing the Zn or Be cell temperatures. Hall effect measurement was performed on as-grown Zn 0.05Be 0.95Te epilayer doped with nitrogen. Hole concentration as high as 2×10 19 cm −3 has been achieved.