Growth characteristics of GaN on (001)GaP substrates by MOVPE

The GaN epilayers are grown on (0 0 1)GaP substrates by low-pressure metalo rganic vapor-phase epitaxy using the three-step growth method, which includ es the growth of the GaN buffer, interlayer and high-temperature epilayer. From atomic force microscopy examinations, it is indicated that the surface roughness of the GaN buffer layer grown at 515 degreesC increases drastica lly with increasing the annealing temperature from 700 degreesC to 850 degr eesC. The thickness and growth temperature of the GaN interlayer were optim ized based on the X-ray and morphology measurements. It was found that a 0. 2-mum-thick GaN interlayer grown at 750 degreesC can efficiently restrict t he desorption of P atoms from the GaP surface, which is an essential step f or the subsequent growth at high temperature (900 degreesC). Furthermore, a s the epilayer thickness increased, the GaN surface became rougher due to t he increase in the composition of the hexagonal component. The 77 K photolu minescence spectrum of the mirror GaN epilayer (0.6 mum in thickness) exhib its a near-band-edge emission peak at 3.36 eV as well as a yellow emission at 2.29 eV. The corresponding electron mobility and carrier concentration a t 300 K were 15 cm(2)/Vs and 6.7 x 10(18) cm (-3), respectively. (C) 2000 E lsevier Science B.V. All rights reserved.