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

Fully strained AlxGa1-xN/GaNAlxGa1-xN/GaN-Bragg-reflectors (DBR) with x>0.4x>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 Al0.21Ga0.79NAl0.21Ga0.79N 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 H2H2 to N2N2 has a significant influence on the growth rates of GaN and AlGaN, we see no impact on the optical properties of the grown structures.