Experimental characterisation of GaN-based resonant cavity light emitting diodes

For the first time, 2λ and 3λ GaN-based microcavities are demonstrated, consisting of a monolithically grown distributed Bragg reflector (DBR) as the first mirror and a metal as the second mirror. The metal acts both as a mirror and electrical contact, emission being through the sapphire substrate. No epitaxial lift-off or dielectric mirrors are required. Reflectance measurements and angle-resolved electroluminescence measurements clearly show the presence of a resonant cavity at wavelengths around 520 nm for the samples presented. At measurement angles off axis, the resonance moves to shorter wavelengths, in agreement with simple theory. Reflectance measurements indicate an effective penetration depth of the optical field into the DBR of approximately 3λ. Design and epitaxy were developed within the EU-funded AGETHA consortium.