Recent advances in III-nitride ultraviolet photonic materials and devices

This paper summarizes some of the recent advances made on III-nitride ultraviolet photonics materials and devices. In particular, the growth and characterization of AlGaN alloys are discussed in detail. It was shown that AlGaN could be made n-type for x up to 1 (pure AlN). Time-resolved photoluminescence (PL) studies carried out on these materials have shown that Si-doping reduces the effect of carrier localization in Al_xGa_1-xN alloys and a sharp drop in carrier localization energy occurs when the Si doping concentration increases above 1 × 10¹⁸ cm^-3, which directly correlates with the observed electrical properties. For the Mg-doped Al_xGa_1-xN alloys, p-type conduction was achieved for x up to 0.27. From the Mg acceptor activation energy as a function of Al content, the resistivity of Mg-doped Al_xGa_1-xN with high Al contents can be estimated. For example, the projected resistivity of Al_xGa_1-xN (x=0.45) is around 2.2 × 10⁴ Ω-cm. Thus alternative methods for acceptor activation in AlGaN or InAlGaN with high Al contents must be developed before the high performance deep UV emitters can be realized.