Interface recombination and carrier confinement at a GaAs/GaxIn1−xP double heterojunction studied by picosecond population modulation spectroscopy

Sensitive picosecond excite-probe modulation methods have been applied to study electron-hole confinement and interface lifetime in a molecular beam epitaxy (MBE) grown n-type GaxIn1−xP/ GaAs/GaxIn1−xP double heterojunction. Time-varying transmission spectra at 77 K have been examined near the E0+Δ0 transition in GaAs and near the fundamental edge in GaxIn1−xP (x = 0.47), following the injection of a small electron-hole population. We demonstrate directly the confining efficiency of the structure for electrons and, consistent with other recent evidence, find that the interface recombination velocity in the relatively strain-free heterostructure is reduced to less than 1×104 cm/s from the value of 5×105 cm/s for a free GaAs surface. The latter has been determined by us directly from time-resolved reflection spectra which suggest further applications of these methods to surface spectroscopy of semiconductors.