Non-polar GaN/AlGaN quantum-well polariton laser at room temperature

Abstract

We demonstrate room temperature (RT) polariton lasing in an all-dielectric microcavity containing non-polar III-nitride quantum wells (QWs) as active media. The microcavity is fabricated using the photo-electrochemical etching method, by which an optimally grown $m$-plane III-nitride active region is detached from the substrate in the form of a membrane, which is subsequently inserted between two $\mathrm{Si}{\mathrm{O}}_{2}/{\mathrm{Ta}}_{2}{\mathrm{O}}_{5}$ distributed Bragg reflectors, with 4 and 10 pairs for the top and bottom mirrors, respectively. The active region consists of 25 $\mathrm{GaN}/{\mathrm{Al}}_{0.1}{\mathrm{Ga}}_{0.9}\mathrm{N}$ (5 nm/3 nm) QWs. The produced microcavities exhibit two closely spaced polarization-resolved lower polariton branches at RT, in line with the selection rules of the non-polar orientation, having a Rabi splitting of 62 and 72 meV in the $E\ensuremath{\parallel}a$ and $E\ensuremath{\parallel}c$ polarizations, respectively. In a positively detuned 3\ensuremath{\lambda}/2-thick microcavity, polariton lasing is observed at ambient conditions in the $E\ensuremath{\parallel}a$ polarization, with a threshold \ensuremath{\sim} 3 times lower than previous state of the art, despite the use of a relatively weak top reflector.