OPTICAL STUDIES OF ZNSE-ZNS GAAS(100) SINGLE QUANTUM-WELLS GROWN BY PHOTO-ASSISTED VAPOR-PHASE EPITAXY/

Confinement effects of phonon and excitonic modes in two monolayers-th ickness ZnSe-ZnS single quantum wells (SQWs) grown through photo-assis ted vapor phase epitaxy (PAVPE) have been investigated by means of Ram an, photoluminescence (PL) and reflection spectroscopy. It has been fo und that the frequency of the SQW longitudinal optical (LO) phonon mod e is red shifted by 2.1cm(-1) relative to the LO phonon frequency of b ulk ZnSe. This shift has been attributed to the combined opposite acti on of strain and confinement effects. The PL data have shown that the Is state of the n = 1 subband heavy-hole (hh) excitonic band is blue s hifted by 188 meV relative to the energy of free excitons in the bulk material. Largely responsible for this shift is the quantum confinemen t of electrons and holes. In addition, the transitions involving the 2 s state of the hh excitons have been clearly observed. The 2s-1s energ y splitting was found to be 38 meV. From this result, the binding ener gy of the Is hh exciton has been estimated to be 44 meV.