We have demonstrated the high-peak-power operation of an AlGaN-based ultraviolet laser diode (UV-LD) with a lasing wavelength of 338.6 nm. The UV-LD structure was fabricated on a bulk GaN(0001) substrate. The broad-area and vertical conductive structure of the UV-LD, whose ridge width and cavity length were 50 and 600 µm, respectively, was employed. The threshold current density and differential external quantum efficiency were estimated to be 38.9 kA/cm2 and 8.5%, respectively. The characteristic temperature of threshold current was estimated to be 119 K, and the temperature dependence of lasing wavelength was obtained to be 0.033 nm K−1. A peak power of over 1 W has been achieved in 338.6 nm under pulsed operation at room temperature, which is the highest peak power ever obtained for AlGaN-based UV-LDs.

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Deep electronic levels of Al x Ga1-x N (0.25<x<0.60) were investigated by deep level transient spectroscopy (DLTS) and photocapacitance methods. Si-doped AlGaN layers were grown on an AlN/sapphire template by metal–organic vapor phase epitaxy. DLTS analysis using a sampling time window of up to 100 s showed two dominant deep levels with activation energies (ΔE) higher than 1.0 eV in Al x Ga1-x N with x=0.25 and 0.37. The densities of those levels were higher than 1×1016 cm-3. For the Al0.60Ga0.40N sample, the deeper levels (ΔE>1.5 eV) were detected by photocapacitance measurement. It was found that the energy position of the dominant deep level closely followed the Fermi level stabilization energy reported by Walukiewicz et al. [J. Cryst. Growth 269 (2004) 119], indicating that the origin of the dominant deep level in AlGaN is related to a defect complex including anti-site defects and divacancies.

SUMMARY Pr:LuAG thin film was deposited by pulsed laser deposition. Before and after thermal treatment, each film was characterized using X‐ray diffraction, scanning electron microscope, and cathode luminescence. Thermal treatment led this film to crystallization of Pr:LuAG with garnet structure. And ultra‐violet (UV) emission was obtained from the Pr:LuAG film pumped by irradiating electron beam. We applied this technique to produce a product of a UV light source using Pr:LuAG thin film target pumped by electron beam.

Chemical and electronic properties of Si-doped AlGaN surfaces with a wide range of Al compositions were investigated. The surface potential of AlGaN increased systematically from 0.9 (for GaN) to 2.6 eV (for Al0.87Ga0.13N), corresponding to the fact that the position of the surface Fermi level (EFsurf) approaches the midgap as the Al composition increases. In addition, the plots of EFsurf position closely follows the Fermi level stabilization energy reported by Walukiewicz et al. [J. Cryst. Growth 269 (2004) 119], indicating that the Fermi level position at the AlGaN surface can be governed by some kinds of surface defect transformations.