Band Offsets in CdZnS/ZnS Strained-Layer Quantum Well and Its Application to UV Laser Diode

Conduction- and valence-band offsets have been estimated as a function of well layer thickness in Cd x Zn 1- x S/ZnS strained-layer superlattices with various compositions using the model-solid theory. Relatively large values of approximately 180-260 meV in the conduction-band offset can be obtained for x =0.2-0.3. The valence-band offset depends strongly on the well layer thickness, while the conduction-band offset is nearly independent of the well layer thickness up to 200 Å. This strained-layer structure was applied to fabricate ultraviolet (UV) laser diodes with multiple quantum wells. Stimulated emission can be observed either under optical pumping at RT or under pulsed injection at 30 K in the spectral range of 357-390 nm. A spectral narrowing in the emission spectrum with increasing current in the UV injection diode was clearly observed in the vicinity of 375 nm at 30 K.