Resonant second-harmonic generation in type-II heterostructures of InP/Al0.48In0.52As.

Abstract

We report an experimental study of the second-harmonic generation in a type-II InP/${\mathrm{Al}}_{0.48}$${\mathrm{In}}_{0.52}$As heterostructure at frequencies of the fundamental beam resonant with the spatially indirect-band-gap transitions. From the comparison between the second-harmonic spectrum of the heterostructure and that of an InP crystal in the region 1.15--1.45 eV, we show an enhancement of the second-order susceptibility in the former that is related to the transitions between electron- and hole-confined states. From a study of the dependence of the second-harmonic generation on the polarization directions and the sample orientation, the symmetry properties of the second-harmonic tensor have been derived. These correspond to a ${\mathit{T}}_{\mathit{d}}$ (bulklike) symmetry class and the data show the predominance, in the visible region, of the contributions to the second-order nonlinear susceptibility coming from transitions involving high-energy nonconfined states. The terms of lower symmetry involving only low-energy confined states give in this case a negligible contribution.