Effects of thermal annealing on photoluminescence and structural properties of (ZnSe)(2)(CdSe)(n) short-period-superlattices multiple quantum wells

This work investigates how thermal annealing affects the optical and struct ural properties of (ZnSe)(2)(CdSe)(n) short-period-superlattices multiple q uantum wells (SPS MQW) grown by molecular beam epitaxy using photoluminesce nce (PL) and high- resolution transmission electron microscopy (HRTEM) tech niques. A characteristic that differentiates annealed SPS MQW from annealed conventional quantum wells is that much greater blueshifts can be observed in annealed SPS MQW as the annealing temperature rises above 400 degrees C . We attribute the larger blueshifts to thermally induced interdiffusion of Zn and Cd atoms between alternate ZnSe and CdSe layers. Furthermore, the P L emission in annealed (ZnSe)(2)(CdSe)(n) SPS MQW quenches at higher temper atures and yields a larger value for the activation energy than in as-grown SPS MQW. HRTEM images of samples annealed at 450 degrees C for 30 min clea rly indicate that SPS structures remain in the quantum well regions of as-g rown SPS MQW, but intermix and disappear in the well regions of annealed (Z nSe)(2)(CdSe)(n) SPS MQW. (C) 1999 American Institute of Physics. [S0021-89 79(99)06004-1].