OPTICALLY DETECTED MAGNETIC RESONANCE (ODMR) IN a-Si

Earlier studies of PL in a-Si : H have shown two resolved bands near 0.9eV and 1.3eV. with strength and peak position dependent on sample preparation. By following the spectral dependence of ODMR in a wide range of glowdischarge (gd) and sputtered (sp) samples, we have shown that the 1.3eV emission has contributions from two distinct components, one of which, near 1.25eV. is associated with pair recombination, and another, near 1.4eV, which shows quenching ODMR signals only, and may be due to excitonic emission. The quenching resonances are identified as electrons and holes occupying tail states, which participate in non-radiative recombination. The 1.25eV emission and 0.9eV emission are both associated with a resonance near g = 2.006, suggesting a radiative dangling bond. The peak energy of these pair emissions is primarily determined by the nature of the hole centre involved

Exciton-related lasing mechanism in ZnSe-(Zn, Cd) Se multiple quantum wells

The processes involved in the stimulated emission by photo pumping in (Zn,Cd)Se-ZnSe multiple quantum wells (MQWs) have been investigated at 77K for a series of different well widths. It has been shown by means of photoluminescence excitation spectroscopy that the confined excitons in the well play an important role in determining the lasing mechanism. The optical gain just above the lasing threshold is attributed to the recombination of an exciton accompanied by emission of one LO phonon. Far above threshold inelastic exciton-exciton scattering processes contribute significantly to the gain