Heavily p-Type Doped ZnSe Using Te and N Co Doping

A lot of progress has been made on the fabrication of solid-state light emitters; however, there is a spectral gap in the green-yellow region (530–590 nm) with all commercially available devices. This spectral region is important for many emerging applications, such as the use of plastic-optical fibers, that require green lasers to achieve the lowest attenuation coefficient. Thus, ZnSe-based devices are still of high interest because, in principle, they can cover the whole spectral region between 490–590 nm. However, successful production of bright, “longlived” laser diodes and light-emitting diodes is tempered by the lack of good p-type ZnSe, among other problems. The use of the ZnSe-Te system for improving the p-type doping has been suggested because ZnTe is an easily doped p-type. The best results so far within such an approach have been obtained by Jung et al., who have reported hole concentrations up to 7 10 cm 3 by using a doped ZnSe/ZnTe:N superlattice. However, because of a large lattice mismatch between the ZnSe and ZnTe ( 7.4%), such a structure tends to form defects, for instance, dislocations, that are detrimental to device operation. Recently, the use of a planar ( -) doping technique has been suggested to reduce the average Te content in the material. In such an approach, ZnSe is codoped with Te and N in delta layers (which do not form full ZnTe monolayers), separated by undoped-ZnSe spacers. The highest achieved net-acceptor concentration (NA ND) is 6 10 cm 3 with an average Te concentration of 1.8% (Table I). In this paper, we report results of photoluminescence (PL) studies of -doped ZnSe with very low Te content but otherwise similar to previously reported samples. We studied two types of samples: the socalled single -doped ( -doping) and triple -doped ( -doping), both of which have Te concentrations as low as about 0.5%.