High-performance EML grown on taper-masked pattern substrates by ultra-low-pressure MOCVD

A novel in-plane bandgap energy controlling technique by ultra-low pressure (22 mbar) selective area growth (SAG) has been developed. To our knowledge, this is the lowest pressure condition during SAG process ever reported. In this work, high crystalline quality InGaAsP-InP MQWs with a photoluminescence (PL) full-width at half-maximum (FWHM) of less than 35meV are selectively grown on mask-patterned planar InP substrates by ultra-low pressure (22 mbar) metal-organic chemical vapor deposition (MOCVD). In order to study the uniformity of the MQWs grown in the selective area, novel tapered masks are designed and used. Through optimizing growth conditions, a wide wavelength shift of over 80 nm with a rather small mask width variation (0-30 mu m) is obtained. The mechanism of ultra-low pressure SAG is detailed by analyzing the effect of various mask designs and quantum well widths. This powerful technique is then applied to fabricate an electroabsorption-modulated laser (EML). Superior device characteristics are achieved, such as a low threshold current of 19mA and an output power of 7mW. (c) 2005 Elsevier B.V. All rights reserved.

Small-signal and large-signal performance test of high-speed optoelectronics devices

This paper presents measurement methods for determining the reflection coefficients and frequency responses of semiconductor laser diodes, photodiodes, and EA modulator chips. A novel method for determining the intrinsic frequency responses of laser diodes is also proposed, and applications of the developed measurement methods are discussed. We demonstrate the compensation of bonding wire on the capacitances of both the submount and the laser diode, and present a method for estimating the potential modulation bandwidth of TO packaging technique. Initial study on removing the effects of test fixture on large-signal performances of optoelectronic devices at high data rate is also given.

Effects of annealing treatment on the formation of CO2 in ZnO thin films grown by metal-organic chemical vapor deposition

Post-growth annealing was carried out on ZnO thin films grown by metal-organic chemical vapor deposition (MOCVD). The grain size of ZnO thin film increases monotonically with annealing temperature. The ZnO thin films were preferential to c-axis oriented after annealing as confirmed by Xray diffraction (XRD) measurements. Fourier transformation infrared transmission measurements showed that ZnO films grown at low temperature contains CO2 molecules after post-growth annealing. A two-step reaction process has been proposed to explain the formation mechanism of CO2, which indicates the possible chemical reaction processes during the metal-organic chemical vapor deposition of ZnO films.

Organic/inorganic hybrid solar cells based on SnS/SnO nanocrystals and MDMO-PPV

SnS/SnO heterojunction structured nanocrystals with zigzag rod-like connected morphology were prepared by using a simple two-step method. Bulk heterojunction solar cells were fabricated using the SnS/SnO nanocrystals blended with poly(2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene) (MDMO-PPV) as the active layer. Compared with solar cells using SnS nanoparticles hybridized with MDMO-PPV as the active layer, the SnS/SnO devices showed better performance, with a power conversion efficiency higher by about one order in magnitude.

PHOTOLUMINESCENCE SPECTRA OF STRAINED HETEROSTRUCTURE OF INP ON GAAS SUBSTRATE GROWN BY METAL-ORGANIC CHEMICAL VAPOR-DEPOSITION

A high-energy shift of the band-band recombination has been observed in photoluminescence spectra of the strained InP layer grown on GaAs substrate. The InP layer is under biaxial compressive strain at temperatures below the growth temperature, because the thermal expansion coefficient of InP is smaller than that of GaAs. The strain value determined by the energy shift of the band-edge peak is in good agreement with the calculated thermal strain. A band to carbon acceptor recombination is also identified.

HIGH-POWER 2-DIMENSIONAL QUANTUM-WIRE LASER ARRAYS

GaAs/AIGaAs two-dimensional quantum-well wire laser arrays fabricated by metal-organic chemical vapour deposition on nonplanar substrates have realised a linear light pulse output Fewer of over 100mW. This is the highest figure reported to date for all kinds of quantum-well wire lasers.

High-performance electroabsorption modulator

A 100-μm-long electroabsorption modulator monolithically integrated with passive waveguides at the input and output ports is fabricated through ion implantation induced quantum well intermixing, using only a two-step low-pressure metal-organic vapor phase epitaxial process. An InGaAsP/InGaAsP intra-step quantum well is introduced to the active region to improve the modulation properties. In the experiment high modulation speed and high extinction ratio are obtained simultaneously, the electrical-to-optical frequency response (E/O response) without any load termination reaches to 22 GHz, and extinction ration is as high as 16 dB.

Zn-doped InGaAs Base Heterojunction Bipolar Transistors Grown by Low Pressure Metal Organic Chemical Vapor Deposition

High performance InP/InGaAs heterojunction bipolar transistors(HBTs) have been widely used in high-speed electronic devices and optoelectronic integrated circuits. InP-based HBTs were fabricated by low pressure metal organic chemical vapor deposition(MOCVD) and wet chemical etching. The sub-collector and collector were grown at 655 ℃ and other layers at 550 ℃. To suppress the Zn out-diffusion in HBT, base layer was grown with a 16-minute growth interruption. Fabricated HBTs with emitter size of 2.5×20 μm~2 showed current gain of 70~90, breakdown voltage(BV_(CE0))>2 V, cut-off frequency(f_T) of 60 GHz and the maximum relaxation frequency(f_(MAX)) of 70 GHz.

Metal-organic Vapor Phase Epitaxy Growth and Characterization of InAlGaN Epilayers

In order to improve crystal quality for growth of quaternary InAlGaN, a series of InAlGaN films were grown on GaN buffer layer under different growth temperatures and carrier gases by low-pressure metal-organic vapor phase epitaxy. Energy dispersive spectroscopy (EDS) was employed to measure the chemical composition of the quaternary, high resolution X-ray diffraction (HRXRD) and photoluminescence (PL) technique were used to characterize structural and optical properties of the epilayers, respectively. The PL spectra of InAlGaN show with and without the broad-deep level emission when only N2 and a N2+H2 mixture were used as carrier gas, respectively. At pressure of 1.01×104 Pa and with mixed gases of nitrogen and hydrogen as carrier gas, different alloy compositions of the films were obtained by changing the growth temperature while keeping the fluxes of precursors of indium (In), aluminum (Al), gallium (Ga) and nitrogen (N2) constant. A combination of HRXRD and PL measurements enable us to explore the relative optimum growth parameters-growth temperature between 850℃ and 870℃,using mixed gas of N2+H2 as carrier gas.

High Power 940 nm Al-free Active Region Laser Diodes and Bars with a Broad Waveguide

The 940 nm Al-free active region laser diodes and bars with a broad waveguide were designed and fabricated. The stuctures were grown by metal organic chemical vapour deposition. The devices show excellent performances. The maximum output power of 6.7 W in the 100 f^m broad-area laser diodes has been measured, and is 2. 5 times higher than that in the Al-containing active region laser diodes with a narrow waveguide and 1. 7 times higher than that in Al-free active region laser diodes with a narrow waveguide. The 19 % fill-factor laser diode bars emit 33 W, and they can operate at 15W with low degradation rates.

High Power 808nm AlGaAs/GaAs Quantum Well Laser Diodes with Broad Waveguide

The 808nm laser diodes with a broad waveguide are designed and fabricated. The thickness of the Al_(0.35)-Ga_(0.65)As waveguide is increased to 0.9μm. In order to suppress the super modes, the thickness of the Al_(0.55)Ga_(0.45)As cladding layers is reduced to only 0.7μm while keeping the transverse radiation losses of the fundamental mode below 0.2cm~(-1). The structures are grown by metal organic chemical vapour deposition. The devices show excellent performances. The maximum output power of 10.2W in the 100μm broad-area laser diodes is obtained.

High temperature operation of 650nm AlGaInP quantum well laser diodes grown by LP-MOCVD

Low threshold current and high temperature operation of 650nm AlGaInP quantum well laser diodes grown by low pressure metal organic chemical vapor deposition (LP-MOCVD) are reported in this paper. 650nm laser diodes with threshold current as low as 22-24mA at room temperature, and the operating temperature over 90 degrees C at CW output power 5 mW were achieved in this study. These lasers are stable during 72 hours burn in under 5mW at 90 degrees C.

High performance 1.55 mu m InGaAsP/InP strained layer quantum well laser diodes fabricated by MOCVD overgrowth method

High performance uncooled 1.55 mu m InGaAsP/InP strained layer quantum well (SL-QW) lasers grown by low pressure metal organic chemical vapor deposition (LP-MOCVD) were reported in this paper. Whole MOCVD over growth method were applied in this work. The threshold currents of 5mA and the highest lasing temperature of 122 degrees C were obtained.

Behavior of Pentacene Initial Nucleation on Various Dielectrics and Its Effect on Carrier Transport in Organic Field-Effect Transistor

The influence of dielectric surface energy on the initial nucleation and the growth of pentacene films as well as the electrical properties of the pentacene-based field-effect transistors are investigated. We have examined a range of organic and inorganic dielectrics with different surface energies, such as polycarbonate/SiO2, polystyrene/SiO2, and PMMA/SiO2 bi-layered dielectrics and also the bare SiO2 dielectric. Atomic force microscopy measurements of sub-monolayer and thick pentacene films indicated that the growth of pentacene film was in Stranski-Kranstanow growth mode on all the dielectrics. However, the initial nucleation density and the size of the first-layered pentacene islands deposited on different dielectrics are drastically influenced by the dielectric surface energy. With the increasing of the surface energy, the nucleation density increased and thus the average size of pentacene islands for the first mono-layer deposition decreased. The performance of fabricated pentacene-based thin film transistors was found to be highly related to nucleation density and the island size of deposited Pentacene film, and it had no relationship to the final particle size of the thick pentacene film. The field effect mobility of the thin film transistor could be achieved as high as 1.38 cm(2)/Vs with on/off ratio over 3 x 10(7) on the PS/SiO2 where the lowest surface energy existed among all the dielectrics. For comparison, the values of mobility and on/off ratio were 0.42 cm(2)/Vs and 1 x 10(6) for thin film transistor deposited directly on bare SiO2 having the highest surface energy.

The role of zinc dopant and the temperature effect on the controlled growth of InNnanorods in metal-organic chemical vapor deposition system

This work was supported by the National Science Foundation of China (60976008 and 60776015), the Special Funds for Major State Basic Research Project (973 program) of China (2006CB604907), and the 863 High Technology R&D Program of China (2007AA03Z402 and 2007AA03Z451). The authors express their appreciations to Prof. Yongliang Li (Analytical and Testing Center, Beijing Normal University) for FE-SEM measurements, to DrTieying Yang and Prof. Huanhua Wang (Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences) for XRD measurements and helpful discussions.