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

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 x 10(-4) Omega cm(2) a re reported. This contact layer is basically dislocation free due to small lattice misfit as long as the thickness is thinner than 500 Angstrom, as co nfirmed by transmission electron microscopy (TEM) observation. The ZnSe lay er serves as a contact layer for BeTe and protecting layer against oxidatio n as well. The electrical properties of the contact layers are strongly dep endent on the ZnSe layer thickness. Au diffusion through the ZnSe layer dow n to the BeTe layer at room temperature is found to be responsible for ohmi c properties. A series of ZnBeTe epilayers with different x values have bee n grown on GaAs by molecular beam epitaxy (MBE). We can easily control the composition by changing the Zn or Be cell temperatures. Hall effect measure ment was performed on as-grown Zn0.05Be0.95 Te epilayer doped with nitrogen . Hole concentration as high as 2 x 10(19) cm(-3) has been achieved. (C) 20 00 Elsevier Science B.V. All rights reserved.