INVITED PAPER Special Issue on Blue Laser Diodes and Related Devices/Technologies Crystalline and Optical Properties of ELO GaN by HVPE Using Tungsten Mask

SUMMARY The epitaxial lateral overgrowth (ELO) of GaN with a stripe tungsten (W) mask pattern is performedby hy- dride vapor phase epitaxy (HVPE) and the crystalline and op- tical properties are investigatedcomparedwith ELO GaN using SiO2 mask by characterizations of X-ray rocking curve (XRC), transmission electron microscopy (TEM) andlow temperature cathodoluminescence (CL). A buried ELO structure of the W mask with a smooth surface is successfully obtained. The tilt of c-axis on the W mask in the ELO GaN is not observed, but in the case of the SiO2 mask, c-axis tilts on the mask region at 1 to 10◦ together with small angle grain boundaries. Half the way from the ELO interface to the surface, the luminescence becomes exci- tonic over the whole lateral extension region, which indicates the optically high crystalline quality of the material. On the other hand, different kinds of luminescence are observed depending on the position. The difference of these luminescence is caused by the defects and/or impurity incorporation on the mask region due to the tilting of c-axis.