Investigation of electrical properties and thermal stability of ohmic contacts to n-ZnSe for planar contacts on blue-green laser diodes

The formation of contacts by means of indium, aluminum, tin and indium-tin-oxide (ITO) to n-type ZnSe layers grown by MBE has been investigated using x-ray-photoelectron- spectroscopy (XPS) and current-voltage (I-V) techniques. Quite different behavior was found for metal contacts compared to ITO. For the latter it is possible to form ohmic contacts for ZnSe doping levels in the range of n equals 2 multiplied by 1017 to 3.5 multiplied by 1018 cm-3 with specific contact resistances as low as Rc equals 9 multiplied by 10-3 (Omega) cm2. Whereas metal contacts behave according to thermionic emission theory with nonlinear I-V-curves depending on the doping level of ZnSe epilayers.