Group III‐nitride distributed Bragg reflectors and resonant cavities grown on bulk GaN crystals by metalorganic vapour phase epitaxy

Abstract

Series of ten-, twenty-, and thirty-period (Al,Ga)N-based distributed Bragg reflectors (DBR) have been grown by low-pressure metalorganic vapour phase epitaxy on bulk GaN substrates. Respective mirror target wavelength reflectances of 54, 72, and 86%, as well as stop band-widths lie in nearly exact agreement with the simulations. The DBR are found to be crack-free if pseudomorphically grown on partially relaxed (Ga,In)N compliance layers. In a second series GaN lambda-cavities are introduced into the mirror structures forming nominally symmetric Fabry-Perot resonators sandwiched either between the air/GaN-interface and an underlying AlxGa1−xN/GaN-Bragg mirror, or sandwiched between a top-and a bottom-DBR with various numbers of AlxGa1−xN/GaN quarter-wave layers. Measured reflectance spectra of samples without top-DBR agree well with the simulations, whereas reflectance spectra of samples with top-DBR remain significantly below the simulations. Upon introduction of AlxGa1−xN/GaN-based bottom-DBR with 90% target wavelength reflectance up to 15.5% light extraction are predicted for encapsulated light emitting diodes. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)