Progress in AlInN-GaN Bragg reflectors: Application to a microcavity light emitting diode
We report on the progress in the growth of highly reflective AlInN-GaN distributed Bragg reflectors deposited by metalorganic vapor phase epitaxy. Al1-xInxN layers with an In content around x similar to 0.17 are lattice-matched to GaN, thus avoiding strain-related issues in the mirror while keeping a high refractive index contrast of about 7%. Consequently, a reflectivity value as high as 99.4% at 450 nm was achieved with a 40-pair crack-free distributed Bragg reflector. We measured an average absorption coefficient alpha [cm(-1)] in the AlInN-GaN Bragg reflectors of 43 +/- 14 cm(-1) at 450 nm and 75 +/- 19 cm(-1) at 400 nm. Application to blue optoelectronics is demonstrated through the growth of an InGaN-GaN microcavity light emitting diode including a 12-pair Al0.82In0.18N-GaN distributed Bragg reflector as bottom mirror. The device exhibits clear microcavity effects, improved directionality in the radiation pattern and an optical output power of 1.7 mW together with a 2.6% external quantum efficiency at 20 mA. (C) 2005 American Institute of Physics.