Application of Wide Gap II–VI Compounds as Emitters and Detectors

Despite the successes reached with wide gap II–VI materials, there is much work to be done in improving these devices in order to increase the lifetime. Two important points in this context that have been investigated in Würzburg are an improvement of p-contacts, which are still not very reproducible, and a decrease of threshold current densities. We show that the formation of Ohmic contacts based on graded ZnSe/ZnTe superlattices is dominated by a diffusion process. Based on these investigations proposals for alternative contacts are made. A decrease of the threshold current density of blue-green laser diodes has been achieved by a modification of the GaAs/ZnSe interface, and values as low as 340 A/cm² have been obtained for simple gain guided structures without facet coating. In addition to emitters, there is a significant potential in the application of wide gap II–VI compounds as detectors in the blue and green spectral region. We describe the first fabrication of such detectors. Although these first devices are not yet optimized, they show a quantum efficiency of several percent in the blue. The spectral response of these devices can be quantitatively described, and based on this understanding proposals for future improvements are made.