Kamata, N.N.KamataKlausing, H.H.KlausingFedler, F.F.FedlerMistele, J.J.MisteleAderhold, J.J.AderholdSemchinova, O.K.O.K.SemchinovaGraul, J.J.GraulSomeya, T.T.SomeyaArakawa, Y.Y.Arakawa2022-03-032022-03-032004https://publica.fraunhofer.de/handle/publica/20667410.1051/epjap:2004128In order to improve the crystal quality of GaN-based light emitting devices, photoluminescence (PL) characterization of below-gap states in plasma assisted MBE-grown GaN / AIGaN quantum well (QW) structures has been done by utilizing a below-gap excitation (BGE) light in addition to an above-gap excitation light. The decrease of the band-edge PL intensity due to the addition of the BGE of 1.17. eV indicates the presence of an energy-matched below-gap state in the two-wavelength excited PL. In continuation to our previous efficiency improvement by applying modulation-doping to GaAs / AIGaAs QW's, we focused on several undoped and Si-doped GaN / AIGaN QW's. Experimental results showed that Si modulation-doping reduces the density of below-gap states in the QW region, hence it is promising for increasing internal quantum efficiency of GaN-based QW's.en674621journal article