H. P. Yang

Low Droop Nonpolar GaN/InGaN Light Emitting Diode Grown on m-Plane GaN Substrate

Low Droop Nonpolar GaN/InGaN Light Emitting Diode Grown on m-Plane GaN Substrate Shih-Pang Chang, Tien-Chang Lu, Li-Fu Zhuo, Chung-Ying Jang, Da-Wei Lin, Hung-Chih Yang, Hao-Chung Kuo, and Shing-Chung Wang Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan Epistar Company Limited, Research and Development Division, Hsinchu 300, Taiwan Institute of Lighting and Energy Photonics, National Chiao Tung University, Tainan County 711, Taiwan

Tunable slow light device using quantum dot semiconductor laser

This investigation experimentally demonstrates a tunable slow light device using a quantum dot (QD) semiconductor laser. The QD semiconductor laser at 1.3 mum fabricated on a GaAs substrate is grown by molecular beam epitaxy. Tunable slow light can be achieved by adjusting the bias current and wavelength detuning. The slow light device operated under probe signal from 5 to 10 GHz is presented. Moreover, we also demonstrate that the tunable slow light device can be used in a subcarrier multiplexed system.

Dynamic characteristics of long-wavelength quantum dot vertical-cavity surface-emitting lasers with light injection.

This investigation experimentally demonstrates the dynamic characteristics of quantum dot vertical-cavity surface-emitting lasers (QD VCSEL) without and with light injection. The QD VCSEL is fully doped structure on GaAs substrate and operates in the 1.3 mum optical communication wavelength. The eye diagram, frequency response, and intermodulation distortion are presented. We also demonstrate that the frequency response enhancement by light injection technique allows us to improve the performance of subcarrier multiplexed system.

Light Output Enhancement of GaN-Based Light-Emitting Diodes by Optimizing SiO2 Nanorod-Array Depth Patterned Sapphire Substrate

In this study, we investigated high-efficiency InGaN/GaN light-emitting diodes (LEDs) grown on sapphire substrates with SiO2 nanorod arrays (NRAs) of different heights. The GaN film showed an improved crystal quality through X-ray diffraction (XRD) full-width at half-maximum (FWHM), photoluminescence (PL), and cathodoluminescence (CL) measurements. The light output power and internal quantum efficiency (IQE) of the fabricated LEDs were increased when compared with those of conventional LEDs. Transmission electron microscopy (TEM) images suggested that the voids between SiO2 nanorods and the stacking faults introduced during the nanoscale epitaxial lateral overgrowth (NELOG) of GaN can effectively reduce the threading dislocation density (TDD). We believe that the improvements could be attributed to both the enhanced light extraction by utilizing SiO2 NRAs and the improved crystal quality through the NELOG method. We found that the sample with SiO2 NRA structures of 200nm height can increase the LED output power by more than 70% in our study. # 2012 The Japan Society of Applied Physics

Tunable Slow Light using Quantum Dot VCSEL for Subcarrier Multiplexed System

We demonstrate that the slow light device can be used in a SCM system for the first time. Tunable slow light can be achieved by adjusting the bias current and wavelength detuning of QD VCSEL.

Modeling of Slow Light in Vertical Cavity Surface Emission Lasers

We develop a model for the slow light in the vertical cavity surface emission lasers (VCSELs), with the combinations of cavity and the population pulsation effects. The dependences of pumping power, injection current and wavelength detuning for the group delays are demonstrated theoretically and experimentally. Up to 65 ps group delays and up to 10 GHz modulation frequency can be achieved in the room temperature at the wavelength of 1.3 mum. Based on the experimental parameters of quantum dot VCSEL structures, we show that the resonance effect of laser cavity plays a significant role to enhance the group delays.

Dynamic characteristics of quantum dot VCSEL with external light injection

This investigation for the first time, experimentally demonstrates the dynamic characteristics of 1.3 mum quantum dot VCSEL without and with external light injection. The eye diagram, frequency response, and intermodulation distortion are presented.

Tunable Optical Delay using Quantum Dot VCSEL by Polarization Control

This study experimentally demonstrates the tunable optical delay using a 1.3 mum quantum dot VCSEL. Tunable optical delays of 42 ps for 10 GHz are achieved by varying the bias current and the signal polarization

Depletion-mode InGaAs/GaAs MOSFET with Oxide Passivated by Amorphous Si

It has been shown that a low interface state density (D(subscript it))＜10^11cm^(-2)ev^(-1) between Ga2O3(Gd2O3) oxide and In0.2Ga0.8 As channel using E-beam evaporation in ultra-high-vacuum(UHV) MBE system made MOSFET successfully fabricated [1,2], However, any oxide without protection will be damaged during device processing, and the device degrades. In this work, the gate oxides Ga2O3(Gd2O3) are capped with amorphous Si prior to removal from the UHV chamber to avoid moisture and other contaminations. A 1.6μm-gate-length depletion-mode GaAs MOSFET with In0.2Ga0.8As/GaAs as channel layers shows a drain current of 370 mA/mm at V(subscript G)=0V. Complete pinch-off at V(subscript G)=-6V and operation in the accumulation mode of up to V(subscript G)=2V are measured. The lower transconductance of 70 mS/mm is due to the higher doping concentration and 540A oxide thickness. However, the transconductance versus gate bias is broader than the best reported data. The device shows hysteresis-free drain current, and high, symmetrical breakdown voltages of 20V.

Singlemode Monolithically Quantum-Dot Vertical-Cavity Surface-Emitting Laser in 1.3 μm with Side-mode Suppression ratio g 30dB

We present monolithically quantum-dot vertical-cavity surface-emitting laser (QD VCSELs) operating in the 1.3 μm optical communication wavelength. The QD VCSELs have adapted fully doped structure on GaAs substrate. The output power is ∼330 μW with slope efficiency of 0.18 W/A at room temperature. Single mode operation was obtained with side-mode suppression ratio of > 30 dB. Modulation bandwidth was also presented for the first time.