Microphotoluminescence studies on GaN‐based airpost pillar microcavities containing InGaN quantum wells and quantum dots

Abstract

We report on the optical properties of monolithic GaN-based airpost pillar microcavities (MCs) with embedded InGaN quantum wells or quantum dots (QDs), respectively. The presented MCs are designed by use of different kinds of distributed Bragg reflectors consisting of either AlGaN/GaN, AlInN/GaN, or superlattices of AlN/InGaN and GaN. A quality factor of up to Q ¼ 260 has been achieved. Airpost pillar MCs, providing a three-dimensional optical confinement, are realized by focused ion beam etching starting from an all-epitaxially grown vertical-cavity surface-emitting laser structure. Pillar diameters below 1 mm are well controllable. The sidewalls are smooth and show a damaged surface layer of a thickness less than 2 nm only. Microphotoluminescence (m-PL) measurements reveal the longitudinal and transversal mode spectra of the cavities in good agreement with theoretical calculations based on a vectorial transfer-matrix method. Furthermore, the spectra of the QD based samples reveal distinct spectrally sharp emission lines around 2.73 eV which can be attributed to the emission of single-InGaN QDs and traced up to 120 K.Scanning electron micrograph of a GaN-based airpost pillar superimposed by the m-PL spectrum of a pillar with a diameter of d ¼ 1.8 mm. The measurement performed at T ¼ 150 K reveals the discrete resonator modes.

Growth and characterization of nitride‐based distributed Bragg reflectors

“…As a consequence, crack‐free DBR samples with a good structural quality were achieved. The optical properties of monolithic microcavities containing QWs and QDs as the active region based on these DBRs are discussed in detail in a recent publication 20.…”

“…The round shape of the measured stop band is an indication for a considerable residual absorption in the structure. Investigations of full cavity structures based on this kind of DBR reveal the SLs to be the main source of the residual absorption 20. By adding In to the SL, the microstructure was improved significantly 21 and the tensile strain of the DBRs relative to a GaN template was reduced.…”

“…By adding In to the SL, the microstructure was improved significantly 21 and the tensile strain of the DBRs relative to a GaN template was reduced. Based on this DBR concept, a monolithic microcavity containing three InGaN QWs was realized showing a quality factor of 250 20.…”

Fabrication of ZnSe‐based microcavities for lasing in the strong coupling regime and polariton confinement

“…Subsequently lasing in the regime of weak and strong coupling has been reported [9]. Advanced dry etching techniques using a focused-ion beam (FIB) [10,11] are available for this material system, which allow for the realization of tailored photonic microstructures, such as micropillars, waveguides or photonic molecules. These structures can be used to investigate the properties confined polariton condensates like their formation, propagation, and spatial as well as temporal coherence.…”