Vertical Cavity InGaN LEDs Grown by MOVPE

Abstract

A RCLED structure, composed of InGaN multi-quantum wells inserted in a 3λ GaN based micro-cavity, was grown by metalorganic vapor phase epitaxy. The bottom mirror was a GaN/AIGaN distributed Bragg reflector (DBR). The growth process was followed by in-situ laser reflectometry, thus allowing an accurate control of the optical thickness (OT) of the various layers in the RCLED structure. We used the 543 nm line of a HeNe laser, and both the DBR and 3λ microcavity were designed at this wavelength. Taking into account the OT decrease after cooling (induced by the thermal lattice contraction and the index decrease), a 3λ cavity at 504 nm (green) was obtained. The emission of the InGaN QWs was found to be detuned with respect to the resonance wavelength. Nevertheless, we observed a resonance effect with an enhanced EL emission near the reflectance dip within the stop-band, the width of the EL peak being as low as 17 nm. The resonance effect was further confirmed by angle-resolved electroluminescence measurements. This work was developed within the framework of the European AGETHA project.