Temperature dependence of the gain in InGaN/GaN quantum wells microlasers grown by MOCVD
Résumé
The integration of nitride semiconductors on a silicon platform is a very promising field for nanophotonic applications in the UV-blue spectral range. Efficient sources are a main topic that can be achieved by compact microlasers based on GaN/AlN and InGaN/GaN multiple quantum wells (MQW) grown on a silicon substrate. The epitaxy of these structures is performed by the controlled-growth of an AlN and GaN buffer layers to prevent from dislocations. To obtain versatile and efficient micro-emitters, the technological development of micro-resonator has been improved for nitride MQW micro-disks on silicon. This unique Nitride-on-Silicon platform has been allowed by releasing the micro-disk membrane with selective under-etching of the silicon substrate. For integrated photonics applications, these micro-disks can be electrically powered but also coupled to optical waveguides to a better extract of the emission. We have already shown that we can reach a few thousand for the quality factor of the microdisks with nitride MQW grown by MBE1 but also in nitride-on-silicon photonic crystal cavities2. The laser emission of the microdisks under optical pumping and at room temperature was obtained over a broad spectral range extending from 275 nm to 470 nm1.
Here we investigate the physics of the micro-resonators with InGaN/GaN MQW grown by MOCVD. Photoluminescence (PL) emission is probed under pulsed optical pumping at 266 nm. Laser emission is reached at room temperature at 390 nm. We focus on the gain properties of the InGaN/GaN MQW active layer. We have investigated the temperature dependence of the microlaser threshold vs temperature. We show that the typical T0 for these microlaser is elevated (T0=77K), meaning that the temperature dependence around room temperature is reduced. We also model the spectra to extract the carrier density at threshold. And we will draw up a comparison with InGaN/GaN MQW microlasers grown by MBE.
References: 1M. Mexis et al., Optics Letters, vol. 36 p.2203 (2011), Sellés et al., APL 109, 231101 (2016) and Sci. Rep. 6, 21650 (2016), 2F. Tabataba-Vakili et al., APL 2017