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 con ditions, and Zn to Se flux ratio on ZnSe: N films were investigated. Z nSe: N films grown at a low substrate temperature of 150-degrees-C usi ng thermally cracked Se had net acceptor concentrations up to 2 X 10(1 8) cm-3 and resulted in the best electrical contact characteristics fo r Au/p-ZnSe. Reliable temperature-dependent Hall measurements were ach ieved using ZnSe: N grown at 150-degrees-C as a contact layer. Delta-d oping experiments showed that the net acceptor concentration can be co ntrolled 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 fix ed active nitrogen flux. Atomic layer epitaxy (ALE) was used to grow C dSe/ZnSe quantum well active layers in LED and laser devices. Laser di odes fabricated from a separate confinement structure (with ALE-grown CdSe/ZnSe single quantum well, ZnSe light-guiding and ZnSSe cladding l ayers) have output powers of 3 mW at 80 K under CW operation. ZnSSe ep ilayers lattice-matched to GaAs were grown directly on GaAs substrates with X-ray rocking curve FWHM as narrow as 20''. The resulting LEDs h ave dramatically prolonged lifetimes, which improve the outlook for pr actical applications.