Fubin Gao

Near infrared electroluminescence from n-InN/p-GaN light-emitting diodes

Undoped InN thin film was grown on p-GaN/Al2O3 (0001) template by molecular beam epitaxy. Near-infrared (NIR) electroluminescence (EL) that overlapped the optical communication wavelength range was realized using the n-InN/p-GaN heterojunction structure. The light emitting diode showed typical rectification characteristics with a turn-on voltage of around 0.8 V. A dominant narrow NIR emission peak was achieved from the InN side under applied forward bias. By comparing with the photoluminescence spectrum, the EL emission peak at 1573 nm was attributed to the band-edge emission of the InN film.

Near infrared electroluminescence from n-InN/p-NiO heterojunction light-emitting diode

The n-InN/p-NiO heterojunction was fabricated by growing an n-type InN film on a c-plane sapphire substrate by plasma-assisted molecular beam epitaxy (PAMBE) and then depositing a p-type NiO film on the InN film by radio frequency (RF) magnetron sputtering. The heterojunction exhibited typical rectification characteristic with a turn-on voltage of ∼1.1 V. A dominant near infrared (NIR) emission was detected from the heterojunction under forward bias. The intensity of the emission increased significantly as the injection current increased from 2 to 10 mA. The NIR emission peaking around 1565 nm was ascribed to the band-edge emission of InN layer based on the photoluminescence spectrum and band diagram of the heterojunction.

Band alignment of InN/6H-SiC heterojunction determined by x-ray photoelectron spectroscopy

The valence band offset (VBO) of InN/6H-SiC heterojunction has been directly measured by x-ray photoelectron spectroscopy. The VBO is determined to be −0.10 ± 0.23 eV and the conduction band offset is deduced to be −2.47 ± 0.23 eV, indicating that the heterojunction has a type-II band alignment. The accurate determination of the valence and conduction band offsets is important for applications and analysis of InN/6H-SiC optoelectronic devices.

Low threshold two-dimensional organic photonic crystal distributed feedback laser with hexagonal symmetry based on SiN

We report on the characterization of low threshold second-order organic photonic crystal distributed feedback laser based on SiN with hexagonal lattice. SiN can increase the index contrast in the photonic crystal distributed feedback as well as the confinement in the waveguide which results in a decrease in the threshold. Low threshold energy of 0.65kW∕cm2 and full width at half maximum of 0.9nm were achieved in lasers. As a result, we observe surface-emitting lasing action and hexagonal emission pattern of side beams whose direction slightly deviates from the normal. We explain the feedback mechanisms by using semiclassical laser theory.

Photoemission spectroscopy study of oxygen spectrum and the chemical failure process of Alq3-based light-emitting devices

Tris (8-hydroxyquinolino) aluminum (Alq3) films and their chemical failure process are investigated using x-ray photoelectron spectroscopy. We make sure that the O 1s spectrum of the pristine Alq3 only has one component which is in contrast to the current controversy on this issue. Our experiments further indicate that the chemical failure process of Alq3 holds the critical role to understand this problem. The chemical failure process also shows the organic carbon contamination and the replacement reaction between Alq3 and water, ultimately resulted in the failure of the device. These fundamental results provide a basis understanding for future development of Alq3-based light emitting devices.

Emission Characteristics and Performance Comparison of Organic Lasers with One-Dimensional Distributed Feedback

This paper presents optically pumped solid-state organic lasers based on tris(8-hydroxyquinoline) aluminum (Alq3) doped with the laser dye 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidy 1-9-enyl)-4H-pyran (DCJTB, 2 wt %) using resonator which offers one dimensional distributed feedback. The lasers have been fabricated by deposition of organic films on top of suitable grating microstructures etched into SiN layer. The devices operating in the red spectral region are highly efficient and exhibit low threshold for oscillation (0.3 kW/cm2). The operating characteristics of the lasers are investigated in detail. The laser oscillation is obtained by optimizing the organic film thickness. The ratio of slot width to grating period is another important parameter to decrease the lasing threshold.