High quality factor nitride-based optical cavities: microdisks with embedded GaN/Al(Ga)N quantum dots

Abstract

We compare the quality factor values of the whispering gallery modes of microdisks (μ-disks) incorporating GaN quantum dots (QDs) grown on AlN and AlGaN barriers by performing room temperature photoluminescence (PL) spectroscopy. The PL measurements show a large number of high Q factor resonant modes on the whole spectrum, which allows us to identify the different radial mode families and to compare them with simulations. We report a considerable improvement of the Q factor, which reflects the etching quality and the relatively low cavity loss by inserting QDs into the cavity. GaN/AlN QDs-based μ-disks show very high Q values (Q>7000) whereas the Q factor is only up to 2000 in μ-disks embedding QDs grown on the AlGaN barrier layer. We attribute this difference to the lower absorption below bandgap for AlN barrier layers at the energies of our experimental investigation.

Dielectric microcavities: Model systems for wave chaos and non-Hermitian physics

“…For a GaAs-disk with a tiny radius 361 nm the quality factor is still around 4000 (Song et al, 2009a). For AlN/AlGaN microdisks of radii 2 − 5 µm the quality factor is ranging from 5000 to 7300 (Mexis et al, 2011). For polymer-based microdisks a quality factor around 6000 has been reported (Lozenko et al, 2012).…”

GaN hemispherical micro-cavities

“…6 Amongst these options, WGM microcavities have been demonstrated as promising candidates for realizing low-threshold lasing with narrow emission linewidths, attributed to their low optical losses and modal volumes. 7,8 However, the superior optical confinement capabilities of GaN WGM microcavities are invariably weakened by optical leakage through its transparent sapphire substrate. Recently, GaN-based undercut two-dimensional (2D) WGM microdisk lasers fabricated through the removal of sacrificial layers embedded within the device structure by photoelectrochemical (PEC) or selective wet-etching [9][10][11] have been reported to effectively reduce such losses.…”

Advances in III‐nitride semiconductor microdisk lasers

“…7, from which a trend can be clearly identified: the QD microdisks have significantly higher Qfactors. Up until now, the record Q-factor of 7300 is observed from AlN microdisk cavities with embedded GaN QDs, while lasing thresholds as low as <60 W/cm 2 has been achieved [51]. A record-low lasing threshold of 0.28 mJ/cm 2 has also been achieved in GaN microdisks with InGaN QDs, with a Q-factor of $6600 [34].…”

“…In addition, due to efficient trapping of the electrically injected carriers within the QDs, the leakage current will be greatly reduced for electrically driven QD lasers [105]. Recent progress of nitride-based microdisk lasers embedded with GaN or InGaN QDs has confirmed some of these anticipations [34,51,106]. A summary of reported Q-factors and thresholds from III-nitride semiconductor microdisks in the past decade using bulk GaN, QWs, and QDs as gain-mediums have been plotted in Fig.…”