Characteristics of free-standing hydride-vapor-phase-epitaxy-grown GaN with very low defect concentration

A free-standing 300-mum-thick GaN template grown by hydride vapor phase epi taxy has been characterized for its structural and optical properties using x-ray diffraction, defect delineation etch followed by imaging with atomic force microscopy, and variable temperature photoluminescence. The Ga face and the N face of the c-plane GaN exhibited a wide variation in terms of th e defect density. The defect concentrations on Ga and N faces were about 5x 10(5) cm(-2) for the former and about 1x10(7) cm(-2) for the latter. The fu ll width at half maximum of the symmetric (0002) x-ray diffraction peak was 69 and 160 arc sec for the Ga and N faces, respectively. That for the asym metric (10-14) peak was 103 and 140 arc sec for Ga and N faces, respectivel y. The donor bound exciton linewidth as measured on the Ga and N faces (aft er a chemical etching to remove the damage) is about 1 meV each at 10 K. In stead of the commonly observed yellow band, this sample displayed a green b and, which is centered at about 2.44 eV. (C) 2000 American Institute of Phy sics. [S0003-6951(00)04649-0].