Electrostatic modulation of excitonic fluid in GaN/AlGaN quantum wells by deposition of few-layer graphene and nickel/gold films

Description

Excitons hosted by GaN/(Al,Ga)N quantum wells (QWs) are spatially indirect due to the giant built-in electricfield that separates electrons and holes along the growth direction. This electric field, and thus exciton energy,can be reduced by depositing metallic layers on the sample surface. Using spatially resolved microphotolu-minescence spectroscopy we compare the effects of two different materials, nickel/gold (NiAu) and few-layergraphene (FLG), on the potential landscape experienced by the excitons. We are able to (i) determine the potentialbarriers imposed on QW excitons by deposition of FLG and NiAu to be 14 and 82 meV, respectively, and(ii) to evince their impact on the exciton transport at appropriate densities. Optical losses and inhomogeneousbroadening induced by deposition of NiAu and FLG layers are similar, and their joined implementation constitutea promising tool for electrostatic modulation of exciton densities even in the absence of any applied electric bias

Abstract

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