Optical emission from ultrathin strained type-II InP/GaP quantum wells

We describe the growth and optical emission from ultrathin strained InP qua ntum wells grown on GaP substrates using gas-source molecular-beam epitaxy. The InP thickness was varied between 0.5 and 1.6 monolayers. Intense photo luminescence was emitted from the structures; time-resolved measurements in dicate rather long carrier lifetimes of about 19 ns. With decreasing InP co verage, the emission lines are shifted from 2.18 to 2.28 eV due to quantum size effects. We explain the emission as spatially indirect recombination o f electrons from the GaP X valleys with holes in InP and its phonon replica s. (C) 2001 American Institute of Physics.