Optical properties of InGaN-based red quantum well and microcavity

Optical properties of InGaN/GaN red quantum well(QW) and their microcavities were studied and compared under optical pumping. Incidence of the excitation laser from the p-side was employed for both structures in order to acquire better emission characteristics. The QW structure was grown on sapphire substrate by metalorganic vapor-phase epitaxy(MOVPE) with a blue pre-layer QW. X-ray and scanning transmission electron microscopy(STEM) measurements demonstrate the good crystalline quality. Emissions from both blue and red QWs were observed and demonstrated to be dominated by radiative recombination. For red InGaN microcavity with two dielectric distributed Bragg reflector(DBR) mirrors, a high Q factor of 2355 at the longitudinal mode of 612.3 nm was achieved. Discrete higher-order modes were also clearly observed, being attributed to the lateral confinement on the photons in the microcavity caused by change in the refractive index of the laser-irradiation area because of the increase of carrier density. The Purcell effect accelerates the radiation recombination rate, leading to the fast decay process in the red InGaN microcavity which does exist for QWs only. Compared with the red QW sample, the emission of red microcavities is much purer and more stable. The above results lay a foundation for the realization of InGaN-based red vertical-cavity surface-emitting lasers(VCSELs) in the future.