Reduction of inhomogeneous broadening of exciton luminescence in CdxZn1-xSe ternary alloys and CdxZn1-xSe-ZnSe multiple quantum wells grown by molecular-beam epitaxy under Se-excess supply

Optical and structural properties of CdxZn1-xSe ternary alloy layers grown by molecular-beam epitaxy (MBE) have been studied as a function of the Se/( Cd, Zn) beam pressure ratio (BPR). With increasing Se/(Cd, Zn) BPR, the inh omogeneous broadening of exciton luminescence and the rms roughness of surf aces decreased drastically. This indicates Ih;lt Se-excess supply during MB E growth-suppresses alloy composition fluctuation and also enhances two-dim ensional growth nucleation. Furthermore, CdxZn1-xSe-ZnSe multiple quantum w ell (MQW) structures have been fabricated under Se-excess supply. Biexciton luminescence from MQW structures was observed, even under a cw weak excita tion condition (less than 100 mW/cm(2)). This observation reflects the find ing that exciton lifetime increase as a result of the improvement of crysta lline quality, which results in the enhancement of carrier accumulation.