Effect of buffer layer growth conditions on the secondary hexagonal phase content in cubic GaN films on GaAs(001) substrates

In this letter, we investigated the effect of the buffer layer growth condi tions on the secondary hexagonal phase content in cubic GaN films on GaAs(0 0 1) substrate. The reflection high-energy electron diffraction (RHEED) pa ttern of the low-temperature GaN buffer layers shows that both the depositi on temperature and time are important in obtaining a smooth surface. Four-c ircle X-ray double-crystal diffraction (XRDCD) reciprocal space mapping was used to study the hexagonal phase inclusions in the cubic GaN (c-GaN) film s grown on the buffer layers. The calculation of the volume contents of the hexagonal phase shows that higher temperature and longer time deposition o f the buffer layer is not preferable for growing pure c-GaN film. Under opt imized condition, 47 meV FWHM of near band gap emission of the c-GaN film w as achieved. (C) 2000 Elsevier Science B.V. All rights reserved.