Optical resonance modes have been observed in optically pumped microdisk cavities fabricated from 50 Å/50 Å GaN/Al x Ga 1Ϫx N(xϳ0.07) and 45 Å/45 Å In x Ga 1Ϫx N/GaN(xϳ0.15) multiple quantum well structures. Microdisks, approximately 9 m in diameter and regularly spaced every 50 m, were formed by an ion beam etch process. Individual disks were pumped at 300 and 10 K with 290 nm laser pulses focused to a spot size much smaller than the disk diameter. Optical modes corresponding to ͑i͒ the radial mode type with a spacing of 49-51 meV ͑both TE and TM͒ and ͑ii͒ the Whispering Gallery mode with a spacing of 15-16 meV were observed in the GaN microdisk cavities. The spacings of these modes are consistent with those expected for modes within a resonant cavity of cylindrical symmetry, refractive index, and dimensions of the microdisks under investigation. The GaN-based microdisk cavity is compared with its GaAs counterpart and implications regarding future GaN-based microdisk lasers are discussed.
Articles you may be interested inMapping of multiple-quantum-well layers and structure of V defects in InGaN/GaN diodes Appl.Theoretical analysis of filamentation and fundamental-mode operation in InGaN quantum well lasers
A set of GaN/AlxGa1−xN(x≈0.2) multiple quantum wells (MQWs) with well widths, Lw, varying from 6 to 48 Å has been grown by metalorganic chemical vapor deposition under the optimal GaN-like growth conditions. Picosecond time-resolved photoluminescence spectroscopy has been employed to probe the well-width dependence of the quantum efficiencies (QE) of these MQWs. Our results have shown that these GaN/AlGaN MQW structures exhibit negligibly small piezoelectric effects and hence enhanced QE. Furthermore, GaN/AlxGa1−xN MQWs with Lw between 12 and 42 Å were observed to provide the highest QE, which can be attributed to the reduced nonradiative recombination rate as well as the improved quantum-well quality. The decreased QE in GaN/AlxGa1−xN MQWs with Lw<12 Å is due to the enhanced carrier leakage to the underlying GaN epilayers, while the decreased QE in MQWs with Lw>42 Å is associated with an increased nonradiative recombination rate as Lw approaching the critical thickness of MQWs. The implications of our results on device applications are also discussed.
An array of GaN hexagonal pyramids with a side length of 8.0 μm was fabricated by selective epitaxial overgrowth. These microsized pyramids are highly efficient microcavities. Three types of optical resonance modes with mode spacings of 10, 5.0, and 6.0 Å were observed when a single pyramid was pumped optically by an intense ultraviolet laser beam. An optical ray tracing method has been developed for calculating the optical resonance modes inside the pyramid microcavities. It was shown that a single pyramidal cavity can support several different types of optical resonance modes. The calculated mode spacing agrees very well with the observations. The uniqueness and advantages of this class of hexagonal pyramidal microcavities over the other microcavities are discussed. The implications of our finding on the future GaN microcavity light emitters including micro-light-emitting diodes, microcavity lasers, and vertical-cavity-surface emitting lasers are also discussed.
Effects of well thickness and Si doping on the optical properties of GaN/AlGaN ͑MQWs͒ have been investigated by picosecond time-resolved photoluminescence ͑PL͒ measurements. Our results have yielded that ͑i͒ the optical transitions in nominally undoped MQWs with narrow well thicknesses (L w Ͻ40 Å) were blue shifted with respect to the GaN epilayer due to quantum confinement, however, no such blue shift was evident for the MQWs with well thicknesses larger than 40 Å, ͑ii͒ the band-to-impurity transitions were the dominant emission lines in nominally undoped MQWs of large well thicknesses (L w Ͼ40 Å) at low temperatures, and ͑iii͒ Si doping improved significantly the crystalline quality of MQWs of large well thicknesses (L w Ͼ40 Å). The implications of these results on the device applications based on III-nitride MQWs have been discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.