Abstract
Scaling-down the size of semiconductor cavity lasers and engineering their electromagnetic environment in the Purcell regime can bring about spectacular advance in nanodevices fabrication. We report here an unprecedented observation of a coherent Cathodoluminescence from GaN nanocavities (20–100 nm). Incident lower energy (< 15 kV) electron beams excite the band edge UV emission from the walls of the network whereas for higher energies, the emitted photons are spontaneously down converted into NIR and preferentially emerge from the nanocavities. Non-centrosymmetric structure of GaN and its nanowall geometry together facilitate this unique observation which is substantiated by our numerical results. At cryogenic temperatures, an intense and narrow laser-like NIR beam emanates out of the nanocavities. The work promises the possibility of fabrication of very high density (over 108/cm2) cavity lasers that are addressable by simple deflection and tuning of incident electron beams.
Highlights
Scaling-down the size of semiconductor cavity lasers and engineering their electromagnetic environment in the Purcell regime can bring about spectacular advance in nanodevices fabrication
One of the best ways of overcoming these challenges is to fabricate laser diodes containing vertical-cavities by vertically distributing semiconductor Bragg reflectors to emit light along the direction normal to the surface of the semiconductor wafer. These Vertical-Cavity Surface Emitting Lasers (VCSELs) have recently attracted a lot of interest and hold edge over other type of lasers because of their high modulation speed at low threshold currents and high quantum efficiency which is primarily due to the small size of the vertical cavities[2,3,4,5]
We present numerical modelling results that support the creation of whispering gallery modes (WGMs) and non-linear frequency conversion
Summary
Scaling-down the size of semiconductor cavity lasers and engineering their electromagnetic environment in the Purcell regime can bring about spectacular advance in nanodevices fabrication. One strand of such research focuses on reduction of physical dimensions of lasers which would result in a scalable nanolaser with increased cavity-emitter interaction (Purcell effect), high integration density and speed, low threshold current and low input power This would require fabrication of small lasers which can confine the carriers and photons within the cavity without additional loss of photons or carriers thereby reducing the cavity round trip time as well as the device capacitance. In previous r eports[8,9], it has been shown that by kinetically controlling the growth parameters for the construction of semiconductor thin films using Molecular Beam Epitaxy (MBE), we can form a very interesting single-crystalline morphology consisting of polygonal shaped cavities bound by steep-wedge shaped nanowalls by a misfit relaxation pathway forming open screw dislocations This porous structure called as a Nanowall Network (NwN) is single crystalline in nature and yields a highly intense band edge emission, with no defect related peaks. The lateral opening width of these cavities can vary from 20 to 200 nm at the top and less than 10 nm at the bottom of the valleys
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