Beryllium Chalcogenides: Interface Properties and Potential for Optoelectronic Applications

Wide bandgap II–VI semiconductors are candidates for optoelectronic applications in the green-blue spectral range. Still existing lifetime problems are at least partly attributed to the high bond polarity and to doping limits of the conventional II–VI compounds, such as ZnSe. Beryllium chalcogenides have a considerable potential to overcome these problems. Therefore, binary, ternary or quaternary Be chalcogenide layers or superlattices may be applied in various regions of optoelectronic devices. We discuss their application as active layers, p-claddings and p-contacts, as well as BeTe-based type-II light emitting diodes. In these heterostructures and superlattices interfaces play a crucial role. Our studies of interface properties focus on the lattice-matched system ZnSe/BeTe, which forms a type-II band alignment with a very high band offset, and on the strongly mismatched system CdSe/BeTe, which forms quantum dots. The experimental methods are Raman spectroscopy of interfacial vibration modes and electromodulation spectroscopy of electronic transitions across the interfaces.