Benjamin Leung

Nonpolar InGaN/GaN Core–Shell Single Nanowire Lasers

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.

Nonpolar InGaN/GaN multi-quantum-well core-shell nanowire lasers

Lasing is demonstrated from nonpolar III-nitride core-shell multi-quantum-well nanowires. The nanowire lasers were fabricated by coupling a top-down and bottom-up methodology and achieved lasing at wavelengths below the GaN bandedge.

Top-down fabrication for III-nitride nanophotonics

III-nitride based nanostructures have gained interest as nanoscale light sources in the UV to visible wavelengths. Here we present a top-down approach to enable vertical, high aspect ratio III-nitride-based nanowires with controllable height, pitch, and diameter. Additionally, through the use of orientation-dependent etch rate measurements, the cross-sections of such nanostructures can be predicted and controlled, which can allow for the manipulation of optical properties. The fabrication and lasing characteristics of GaN-based nanowires fabricated by this approach will be presented, along with schemes for single optical mode selection, polarization control, beam shaping, and wavelength tuning. Finally, we present a new method for the etching of size-controlled InGaN quantum dots (QDs) using quantum size effects.

III-Nitride nanowires lasers

Nanowires have gained interest as coherent, nanoscale light sources. Using a top-down approach, high quality III-nitride-based nanowires with controllable height, pitch and diameter have been realized. Here, the fabrication, and lasing characteristics of GaN-based and GaN/InGaN based nanowires fabricated by this approach will be presented, along with schemes for single optical mode selection, polarization control, beam shaping, and wavelength tuning.

Electrically Injected UV-Visible Nanowire Lasers

There is strong interest in minimizing the volume of lasers to enable ultracompact, low-power, coherent light sources. Nanowires represent an ideal candidate for such nanolasers as stand-alone optical cavities and gain media, and optically pumped nanowire lasing has been demonstrated in several semiconductor systems. Electrically injected nanowire lasers are needed to realize actual working devices but have been elusive due to limitations of current methods to address the requirement for nanowire device heterostructures with high material quality, controlled doping and geometry, low optical loss, and efficient carrier injection. In this project we proposed to demonstrate electrically injected single nanowire lasers emitting in the important UV to visible wavelengths. Our approach to simultaneously address these challenges is based on high quality III-nitride nanowire device heterostructures with precisely controlled geometries and strong gain and mode confinement to minimize lasing thresholds, enabled by a unique top-down nanowire fabrication technique.