RECENT DEVELOPMENTS IN THE MBE GROWTH OF WIDE BANDGAP II-VI SEMICONDUCTORS FOR LASER-DIODES AND LEDS

We have studied the p-type doping of ZnSe, using active nitrogen. The effects of growth conditions such as substrate temperature, plasma conditions, and Zn to Se flux ratio on ZnSe: N films were investigated. ZnSe: N films grown at a low substrate temperature of 150-degrees-C using thermally cracked Se had net acceptor concentrations up to 2 X 10(18) cm-3 and resulted in the best electrical contact characteristics for Au/p-ZnSe. Reliable temperature-dependent Hall measurements were achieved using ZnSe: N grown at 150-degrees-C as a contact layer. Delta-doping experiments showed that the net acceptor concentration can be controlled from 1 X 10(18) to 1 X 10(17) CM-3 when the ZnSe surface for nitrogen incorporation was changed from Zn- to Se-stabilized for a fixed active nitrogen flux. Atomic layer epitaxy (ALE) was used to grow CdSe/ZnSe quantum well active layers in LED and laser devices. Laser diodes fabricated from a separate confinement structure (with ALE-grown CdSe/ZnSe single quantum well, ZnSe light-guiding and ZnSSe cladding layers) have output powers of 3 mW at 80 K under CW operation. ZnSSe epilayers lattice-matched to GaAs were grown directly on GaAs substrates with X-ray rocking curve FWHM as narrow as 20''. The resulting LEDs have dramatically prolonged lifetimes, which improve the outlook for practical applications.