Photoreflectance investigations of the bowing parameter in AlGaN alloys lattice-matched to GaN

Room temperature photoreflectance investigations have been performed on a s eries of AlGaN layers grown both by metalorganic vapor phase epitaxy and mo lecular beam epitaxy on c-plane sapphire substrates. The aluminum compositi on was ranging between 0% and 20%, and was determined independently in the different growth laboratories, by various methods. It is found that within the experimental uncertainty, there is no detectable bowing parameter in th ese alloys. This contradicts some previous experimental investigations and confirms other ones. (C) 1999 American Institute of Physics. [S0003-6951(99 )01122-5].