Optical and structural studies of the effect of spacers in modulation-doped ZnSe/Zn1-xCdxSe quantum wells

The effect of spacers in modulation-doped Zn1-xCdxSe/ZnSe:Cl multiple quant um wells (MD-MQWs) was investigated by photoluminescence (PL) and time-of-f light secondary-ion-mass spectrometry (TOF-SIMS). A comparison was made bet ween structures with and without spacers as a function of annealing tempera ture. The diffusion of Cl and Cd was monitored by TOF-SIMS depth profiling and photoluminescence. Although TOF-SIMS does not show any significant diff usion of Cl and Cd in both structures at temperatures up to 385 degrees C, the PL results indicate the modification of optical properties in the Zn1-x CdxSe/ZnSe:Cl MD-MQWs due to annealing. Up to an annealing temperature of 3 85 degrees C, the MD-MQWs with spacers show superior optical quality in the quantum well regions, while quenching of the quantum well band-edge PL and strong enhancement of deep-level emission were observed from the MD-MQWs w ithout spacers. This phenomenon suggests that the radiative deep-level emis sion may provide more efficient channel for electron-hole recombination wit h increasing annealing temperature. (C) 1999 American Institute of Physics. [S0021-8979(99)01114-7].