Progress in AlInN–GaN Bragg reflectors: Application to a microcavity light emitting diode

Abstract

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∼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 450nm was achieved with a 40-pair crack-free distributed Bragg reflector. We measured an average absorption coefficient α[cm−1] in the AlInN–GaN Bragg reflectors of 43±14cm−1 at 450nm and 75±19cm−1 at 400nm. 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 1.7mW together with a 2.6% external quantum efficiency at 20mA.