A molybdenum (Mo)-doped zinc oxide thin film is deposited on a glass substrate by a rf magnetron sputtering technique. The structural and optical characteristics of ZnO:Mo (ZMO) thin films prepared with various deposition parameters are investigated. A series of SEM images obtained reveal that the average grain size of ZMO thin films is small and uniform. Energy dispersive spectroscopy analysis also verifies that traces of Mo are present in the as-grown thin films. The thicknesses of these ZMO films ranging from 150 to 390 nm are obtained by varying pertinent sputtering parameters. The average transmittance of ZMO thin films measured is more than 80% in the visible spectrum.
High-temperature stability of lasing wavelength of GaAsSb/GaAs quantum well (QW) lasers grown by metal-organic
vapor phase epitaxy will be demonstrated. According to the best of our knowledge, this is the first trial of using
triethylgallium (TEGa) as the precursor to grow QW at low temperature (525°C). The lasing wavelength ranges from
1117 to 1144 nm and varies with temperature (dλ/dT) from 0.24 to 0.287 nm/K. These values are lower than other
previously reported results. The QW grown at high temperature (600 °C) by using trimethylgallium (TMGa) is also
examined. The lasing wavelength is 1125.6 nm at room temperature and dλ/dT is 0.36 nm/K, which is higher than those
lasers grown at lower temperature.
The RF-sputtered ITO layers were used as the transparency contact layer of the MSM PDs. The plasma gas would alter
the optical transmittance and the schottky barrier height between the ITO layer and InGaAsN absorption layer. Three
kinds of plasma gases were studied including Ar, Ar/N2, and Ar/O2. The Schottky barrier heights were 0.510 eV, 0.572
eV, and 0.574 eV when using Ar, (Ar/N2), and (Ar/O2) as the plasma gas; besides, the optical transmittances were
92.56%, 93.12% and 96%, respectively. Although the ITO film sputtered in the Ar/O2 ambient has highest transmittance
and Schottky barrier height, the high resistivity limited the photocurrent of the photodetectors; it is almost three orders
lower than the others. Consequently, using the Ar/N2 as the plasma gas would be a suitable choice regarding the MSM
photodetector application. The highest contrast ratio between photo-current and dark-current of the InGaAsN MSM
photodetectors were 5, 25 and 12 (measured under 0.2V) using Ar, Ar/N2, and Ar/O2 as the plasma gases.
The fabrication and characterization of the p-i-n optical waveguide modulators on silicon-on-insulator (SOI) substrate
were demonstrated. The modulation was based on the mechanism of carrier injection, or plasma dispersion effect. The
corresponding p and n regions were defined in both types of silicon substrates (conventional p-doped and highly resistive
SOI substrates with respective resistivities of &rgr;~7-10&OHgr;-cm and &rgr;~7000-10000&OHgr;-cm) using the spin-on-dopant (SOD)
technique. The SOD diffusion process was conducted at 900-1000°C in nitrogen ambient. The diffusion time and
temperature, and the resistivity of SOI substrate used were the primary parameters dictating the resultant dopant
concentrations and diffusion depths. For the modulators fabricated with various waveguide widths and electrode lengths,
the corresponding modulation index was enhanced in response to an increase in the electrode (or modulation) length
and/or a decrease in waveguide width. The highest modulation index of ~4.15% was successfully achieved for a silicon
p-i-n waveguide modulator with 5&mgr;m,wide waveguide and 7mm-long modulation electrode.
Thermal management is now a critical problem for applications of high power light emitting diodes (LEDs).
This paper develops a novel LEDs (Fig.1a) package technique that can overcome thermal problem, and the
ability to drive the red LEDs at higher power. Copper is plated on the AlInGaP-based red LED chip directly, and
the thermal resistance from chip to the metal heat sink is decreased greatly. With the copper plating layer, the
working current of the AlInGaP-based red LED can be increased from conventional 350 mA to 1650mA in room
temperature. It was found that the luminous intensity at 350 and 1050 mA of the novel package LEDs showed
53% and 431% enhancement as compared with those of the conventional package ones (Fig.1b). The electrical
and optical characteristics of two kind's packages were shown in Figure 2 and Figure 3, respectively.
Recently, GaAs-based long wavelength lasers have attracted much attention owing to their advantages such as low
substrate cost, mature AlGaAs/GaAs DBR and the high conduction band offset. Among the GaAs-based material system,
highly compressive strained InGaAs would be a suitable candidate for the 1300nm VCSEL application while combined
with the large gain-cavity detuning technique. In this work, we have successfully fabricated the highly compressivestrained
InGaAs broad-area lasers grown by MOVPE. After optimized the epitaxial parameters, these lasers were
operating at 1219.56nm with narrow line width of 0.08nm. The InGaAs laser could be operated under continuously
waving (CW) situation at 20°C, while its threshold current density Jth was 140A/cm2. To our knowledge, the
demonstrated InGaAs QW laser has the lowest Jth/QW =46.7 A/cm2. The fitted characteristic temperature (T0) was
146.2K indicating the good electron confinement ability. In addition, by lowering the growth temperature to 475°C, we
have also obtained the InGaAs/GaAs double quantum wells whose PL peak was at 1244.5nm and FWHM was 43meV.
These good characteristics indicate the possibility of fabricating InGaAs VCSELs lasing at 1300nm.
The Jet Propulsion Laboratory (JPL) is developing a 512x640-format, dual broadband, Quanum Well Infrared Photodetector (QWIP) focal plane array (FPA) for an imaging interferometer. This is a new type of imaging interferometer which is based on special Fourier-transform spectroscopy, scans interferograms digitally without moving any optical components. It is stable enough to measure fluctuating target signatures from unstable platforms, making it ideal for detecting chemical agents from a remotely piloted aircraft. These static interferometers require large-format FPAs with high uniformity and operability. QWIP technology is ideal for this instrument because it has achieved remarkable success in advancing highly uniform, highly-operability, and large-format multicolor FPAs. The FPA used in the interferometer covers the wavelength from 6-10 μm and 10-15 μm in alternative rows.