Strain compensated AlGaN/GaN-Bragg-reflectors with high Al content grown by MOVPE

Abstract

Fully strained Al x Ga 1 - x N/GaN -Bragg-reflectors (DBR) with x > 0.4 have been grown on (0 0 0 1) sapphire by metalorganic vapour phase epitaxy. We report on the fabrication of strain compensated DBR structures with a stop band in the blue green spectral region by using an underlying Al 0.21 Ga 0.79 N buffer layer. For a reactor pressure of 50 Torr and a N/III ratio of less than 800 we were able to find a growth regime where parasitic prereactions of the precursors were neglected. Although a change in atmospheric composition from H 2 to N 2 has a significant influence on the growth rates of GaN and AlGaN, we see no impact on the optical properties of the grown structures.