Effect of native defects on optical properties of InxGa1-xN alloys

Materials Sciences Division, Lawrence Berkeley National Laboratory and Department of Materials Science and Engineering, University of California, Berkeley, California 94720
Applied Physics Letters (Impact Factor: 3.52). 11/2005; DOI: 10.1063/1.2108118
Source: IEEE Xplore

ABSTRACT The energy position of the optical-absorption edge and the free-carrier populations in In x Ga 1-x N ternary alloys can be controlled using high-energy 4 He + irradiation. The blueshift of the absorption edge after irradiation in In-rich material (x≫0.34) is attributed to the band-filling effect (Burstein-Moss shift) due to the native donors introduced by the irradiation. In Ga-rich material, optical-absorption measurements show that the irradiation-introduced native defects are inside the band gap, where they are incorporated as acceptors. The observed irradiation-produced changes in the optical-absorption edge and the carrier populations in In x Ga 1-x N are in excellent agreement with the predictions of the amphoteric defect model.

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    ABSTRACT: We have performed systematic studies of the effects of high-energy particle irradiation on the properties of InGaN alloys. In agreement with the amphoteric defect model, irradiation of InN produces donor-like defects. The electron concentration increases with increasing radiation dose and saturates at 4×1020cm−3 at very high doses. We find that the increase of the electron concentration causes a large blue-shift of the absorption edge, which is well explained by the Burstein–Moss effect. The maximum electron concentration decreases with increasing Ga fraction in irradiated In1−xGaxN alloys as the conduction band edge approaches the Fermi level stabilization energy (EFS). For x>0.66 the conduction band edge moves above EFS and the irradiation of n-type films produces acceptor-like defects, resulting in a reduced free electron concentration. An analysis of the concentration dependence of the electron mobility in InN indicates that the dominant defects in irradiated InN are triply charged donors. Finally, we show that InN films doped with Mg acceptors behave like undoped films above a threshold radiation dose.
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