Yun-Jing Li

Fabrication and luminescent properties of core-shell InGaN/GaN multiple quantum wells on GaN nanopillars

Core-shell InGaN/GaN multiple quantum wells (MQWs) on GaN nanopillars were fabricated by top-down etching followed by epitaxial regrowth. The regrowth formed hexagonal sidewalls and pyramids on the nanopillars. The cathodoluminescence of MQWs blue shifts as the location moves from top to bottom on both the pillar sidewalls and pyramid facets, covering a spectral linewidth of about 100 nm. The MQWs on the pillar sidewalls have a higher InN fraction than those on the pyramid facets. The photoluminescent wavelength is stable over two orders of carrier density change due to the smaller quantum confined Stark effect on the nanopillar facets.

InGaN/GaN multiple-quantum-well nanopyramid-on-pillar light-emitting diodes

We report the study of an electrically driven nanopyramid-on-pillar green light-emitting diode (LED). The pyramid-on-pillar nanostructure was fabricated by top-down etching from a GaN template, followed by epitaxial regrowth. High-In-content InGaN/GaN multiple quantum wells (MQWs) were grown on semipolar pyramid and nonpolar pillar surfaces. The measured radiative lifetimes of MQWs on these two surfaces were 2 orders of magnitude shorter than that of a conventional c-plane (0001) MQW owing to their lower polarization field. Electrical injection performance was also demonstrated and discussed.

Resonant modes of 12-fold symmetric defect free photonic quasicrystal

This work investigates the resonant modes of a 12-fold symmetric defect free photonic quasicrystal (PQC) nanorod array using finite difference time domain (FDTD) simulation. Localized modes can exist in PQC without introducing defects due to the lack of translational symmetry. The resonant modes of the unit cell PQC and the one time expanded PQC from unit cell are systematically examined. The resonant spectrum is that of a single rod modified by the interaction among PQC nanorods. The mode confinement is contributed by guided resonance and destructive interference scattering. The self-scaling similarity of resonant spectrum and mode profile are also investigated.

Coreshell InGaN/GaN MQW nanorod photovoltaic device

We report the fabrication and study of coreshell InGaN/GaN multiple quantum well (MQW) nanorod photovoltaic device. The nanorods were fabricated from a GaN substrate by top-down etch, followed by InGaN/GaN MQW growth. The 3D geometry allows higher Indium incorporation and extends the solar absorption spectral range as compared with a planar reference sample. The proof-of-concept coreshell nanorod photovoltaic device has a fill factor of about 54.2%, the short current density of 1.16 mA/cm2, the open circuit voltage of 0.68 V, and the power conversion efficiency of 0.38%, respectively.

Multifacet Microrod Light-Emitting Diode With Full Visible Spectrum Emission

We demonstrated a full visible spectrum emission from a 3D multifacet microrod light-emitting diode (LED). The microrods were fabricated by top-down patterned etched and regrowth. Hexagonal {11-20} and {11-22} facets were first formed on the microrods, then gradually transformed to {10-10} and {10-11} facets. This facet evolution was attributed to the growth competition among different crystal planes. The multiple quantum wells grown on the microrods also followed this facet evolution and resulted in broad emission spectrum. The device can have direct white light emission covering full visible spectral range from 460 to 660 nm under electrical injection.

The crystalline and optical properties of (1122) semipolar GaN and InGaN/GaN MQWs on (1100) M-sapphire

We report the growth temperature effect on the crystalline and optical properties of (112̅2) semipolar GaN and InGaN/GaN MQWs. It shows that a lower growth temperature at 1020 °C produces better crystalline and optical properties.

Photoluminescent study of high indium content nanopyramid light emitting diodes

The radiative and non-radiative lifetime of high In content nanopyramid GaN LEDs are investigated by time resolved and temperature dependent photoluminescent measurement. The radiative recombination efficiency is much improved compared with the conventional c-plane LED.

Low efficiency droop of InGaN/GaN blue LEDs with super-lattice active structure

Department of Photonics & Institute of Electro-Optical Engineering, National Chiao Tung University, 1001 Ta Hsueh Rd., Hsinchu 300, Taiwan R&D Division, Epistar Co. Ltd., Science-based Industrial Park, Hsinchu 300, Taiwan Department of Electronic Engineering, National Chiao Tung University, 1001 Ta Hsueh Rd., Hsinchu 300, Taiwan Institute of Lighting and Energy Photonics, National Chiao Tung University at Tainan, Taiwan Phone: +886-3-5712121, Fax: +886-3-5716631, E-mail: SPC@epistar.com.tw