Recombination dynamics in n-AlxGa1-xAs/n-In0.5Ga0.5P type-II heterostructures

Abstract

Recombination characteristics of n-AlxGa1-xAs/n-In0.5Ga0.5P type-II band line-up heterostructures are investigated using time-integrated and time-resolved photoluminescence (PL) measurements. It is observed that the decay time of the AlxGa1-xAs luminescence depends on whether or not the excitation photon energy, (h) over bar omega(e), is larger than the In0.5Ga0.5P band-gap energy, E-g,E-InGaP. If (h) over bar omega(e) >E-g,E-InGaP, photoexcited holes in the AlxGa1-xAs and In0.5Ga0.5P layers are found to be in equilibrium within about 0.4 ns. The interface-related below-band-gap (BBG) PL shows a large blueshift as the excitation intensity is increased. The extremely long decay time of the BBG PL is attributed to the somewhat smaller wave function overlap between spatially separated, two-dimensional electrons and holes due mainly to the nonabrupt interfacial nature of the employed samples. The fast transient behavior of the BBG luminescence under high excitation intensity, as well as the peak energy blueshift, are explained by the band filling effect. (C) 1998 American Institute of Physics. [S0003-6951(98)00635-4].