Optical induced blueshift of PLE spectrum improvement in n-i-p-i multiple quantum well structures

A large blue shift in the peak position of the photoluminescence excitation (PLE) spectra of n-i-p-i MQW structures have been observed when the excitation power intensity is varied from /spl sim/ 1 mW/cm/sup 2/ to /spl sim/10 W/cm/sup 2/. With multiple step-quantum wells (MS-QWs), the blue shift is found to be much larger than that of the n-i-p-i MQWs structure with normal rectangular quantum wells. The blue shift is found to be dependent on the excitation intensity I/sup ex/ in the form /spl Delta/h/spl nu//sub max/ - /spl Delta/h/spl nu//sub max/ / 1 + (I/sup ex//I/sup a/)/sup s/.