INTENSITY-DEPENDENT ENERGY AND LINESHAPE VARIATION OF DONOR-ACCEPTOR-PAIR BANDS IN HIGHLY COMPENSATED ZNSE-N

The photoluminescence (PL) of donor-acceptor-pairs (DAP) in ZnSe:N/GaA s epilayers at different levels of nitrogen doping and various compens ation ratios is studied. The PL spectra of moderately doped and weakly compensated samples show a DAP zero-phonon line and clearly distingui shed phonon replica shifting to the red by 10 meV for strongly decreas ing excitation density. At medium nitrogen doping and compensation lev el, well-structured, but red-shifted and broadened DAP emission shows a more pronounced dependence on excitation density. For highly doped a nd strongly compensated samples, the DAP band continuously develops fr om a structureless red-shifted broad emission to a well-structured one for increasing excitation density. More heavily doped and strongly co mpensated samples show strongly red-shifted and structureless broad ba nd emissions for all excitation densities, and a very pronounced depen dence of the maximum position on excitation density. We present a gene ral explanation by charged impurities randomly distributed in highly c ompensated samples and causing a fluctuating potential affecting the b ands and impurity levels.