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Nonpolar InGaN/GaN Core-Shell Single Nanowire Lasers

Nano Letters

Li, Changyi; Wright, Jeremy B.; Liu, Sheng L.; Lu, Ping L.; Figiel, J.J.; Leung, Benjamin; Chow, Weng W.; Brener, Igal B.; Koleske, Daniel K.; Luk, Ting S.; Feezell, Daniel F.; Brueck, S.R.J.; Wang, George T.

We report lasing from nonpolar p-i-n InGaN/GaN multi-quantum well core-shell single-nanowire lasers by optical pumping at room temperature. The nanowire lasers were fabricated using a hybrid approach consisting of a top-down two-step etch process followed by a bottom-up regrowth process, enabling precise geometrical control and high material gain and optical confinement. The modal gain spectra and the gain curves of the core-shell nanowire lasers were measured using micro-photoluminescence and analyzed using the Hakki-Paoli method. Significantly lower lasing thresholds due to high optical gain were measured compared to previously reported semipolar InGaN/GaN core-shell nanowires, despite significantly shorter cavity lengths and reduced active region volume. Mode simulations show that due to the core-shell architecture, annular-shaped modes have higher optical confinement than solid transverse modes. The results show the viability of this p-i-n nonpolar core-shell nanowire architecture, previously investigated for next-generation light-emitting diodes, as low-threshold, coherent UV-visible nanoscale light emitters, and open a route toward monolithic, integrable, electrically injected single-nanowire lasers operating at room temperature.

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TYPE Journal Article YEAR 2017
ScopusOSTIDOI

Intrinsic polarization control in rectangular GaN nanowire lasers

Nanoscale

Li, Changyi; Liu, Sheng L.; Luk, Ting S.; Figiel, J.J.; Brener, Igal B.; Brueck, S.R.J.; Wang, George T.

We demonstrate intrinsic, linearly polarized lasing from single GaN nanowires using cross-sectional shape control. A two-step top-down fabrication approach was employed to create straight nanowires with controllable rectangular cross-sections. A clear lasing threshold of 444 kW cm-2 and a narrow spectral line width of 0.16 nm were observed under optical pumping at room temperature, indicating the onset of lasing. The polarization was along the short dimension (y-direction) of the nanowire due to the higher transverse confinement factors for y-polarized transverse modes resulting from the rectangular nanowire cross-section. The results show that cross-sectioned shape control can enable inherent control over the polarization of nanowire lasers without additional environment requirements, such as placement onto lossy substrates.

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TYPE Journal Article YEAR 2016
ScopusOSTIDOI

Electronic transport through Al/InN nanowire/Al junctions

Applied Physics Letters

Lu, Tzu-Ming L.; Wang, George T.; Pan, Wei P.; Zhao, S.; Mi, Z.

We report non-linear electronic transport measurement of Al/Si-doped n-type InN nanowire/Al junctions performed at T = 0.3 K, below the superconducting transition temperature of the Al electrodes. The proximity effect is observed in these devices through a strong dip in resistance at zero bias. In addition to the resistance dip at zero bias, several resistance peaks can be identified at bias voltages above the superconducting gap of the electrodes, while no resistance dip is observed at the superconducting gap. The resistance peaks disappear as the Al electrodes turn normal beyond the critical magnetic field except one which remains visible at fields several times higher than critical magnetic field. An unexpected non-monotonic magnetic field dependence of the peak position is observed. We discuss the physical origin of these observations and propose that the resistance peaks could be the McMillan-Rowell oscillations arising from different closed paths localized near different regions of the junctions.

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TYPE Journal Article YEAR 2016
ScopusOSTIDOI
Results 76–100 of 254
Results 76–100 of 254