p - n junction zinc sulfo-selenide and zinc selenide light-emitting diodes

The wide-band-gap group II–group VI compound semiconductors have long been valued for their luminous efficiency, and an obvious application would be p-n junction LED’s. However, these materials could only be made n type, not p type. Using an uncustomary technique, we have succeeded in making stable low-resistivity p-type ZnSxSe1−x and ZnSe by diffusion into n-type substrates, and thereby have made low-resistance LED’s. The diffusion process is carried out in two steps: a deposition step followed by a drive-in. Gallium, indium, and thallium are used to make the material p type. (i) The group IIIA element is present in doping quantities only. (ii) p-type mobility values are presented as a function of hole concentration; temperature dependence establishes that the level is shallow. (iii) The LED’s have low resistance and the light output is linear with current above the barrier voltage. (iv) Generation current from the junction, n=2, is observed below the barrier voltage. External quantum efficiencies around 1% are estimated with optimized diodes.