engleski

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~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&plusmn ; ; 14 cm– 1 at 450 nm and 75&plusmn ; ; 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.

GaN; Bragg refectors; MOCVD

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