Influence of GaN template thickness and morphology on AlxGa1−xN luminescence properties

We report on Al_xGa_1−xN/GaN films grown by atmospheric pressure MOVPE in a home-made vertical reactor. The high temperature GaN template is grown using the Si/N treatment of (0 0 0 1) sapphire substrate. This process presents advantages of ELO technology without its ex-situ complicated steps and induces 3D (initial stage) to 2D growth mode. We investigate systematically the effect of the template thickness and morphology on optical properties of the AlGaN films by photoluminescence (PL) measurements. Four 0.5 μm-thick Al_0.07Ga_0.93N samples on different GaN templates have been studied. PL spectra, dominated at low temperature by the donor bound exciton emission line, show a better film quality when AlGaN is grown on 1.3 μm-thick high quality 2D GaN template. Two quenching mechanisms of the donor bound exciton PL-intensity are discussed. The PL peak linewidth increases as a function of Al composition. A bowing parameter of 0.93 eV is obtained from the band gap variations as a function of Al composition.

Highlights

► Al_xGa_1−xN was grown on different GaN templates.

► Better luminescence property is obtained with 1.3 μm-thick GaN template.

► Alloy disorder induces PL peak linewidth increase.

► A bowing parameter of 0.93 eV is obtained.

► Two quenching mechanisms of the donor bound exciton PL-intensity are discussed.

Source:Optical Materials

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