Broadband MMIC Power Amplifier for C-X-Ku-Band Applications

A three-stage MMIC power amplifier operating from 6to 18GHz is fabricated using 0.25μm A1GaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor（PHEMT）.The amplifier isfully monolithic,with all matching,biasing,and DC block circuitry included on the chip.Thepower amplifier has an average power gain of 19dB over 6～18GHz.At operation frequenciesfrom 6 to 18GHz,the output power is above 33.3dBm,and the maximum output power of the MMICis 34.7dBm at 10Ghz.The input return loss is less than-10db and the out-put return is lessthan-6dB over operating frequency.This power amplifier has,to our knowledge,the best powergain flatness reported at C-X-Ku-band applications.

HIGH-ENERGY PROTON IRRADIATION EFFECTS ON GaAs/Ge SPACE SOLAR CELLS

This paper reports the high-energy proton irradiation effects on GaAs/Ge space solar cells. The solar cells were irradiated by protons with energy of 5-20 MeV at fluence ranging from 1×109 to 7×1013 cm-2, and then their electric parameters were measured at AM0. It was shown that the Isc, Voc and Pmax decrease as the proton energy increasing, and the degradation is relative to proton irradiation-induced defect with a level of Ec-0.41 eV in irradiated GaAs/Ge cells.

High Quality Zinc Sulfide Epitaxial Layers Grown by Metalorganic Chemical Vapour Deposition

ZnS films were successfully grown by metallorganic chemical vapour deposition (MOCVD) at atmospheric pressure on (100) GaAs substrates. The deposition was carried out at a substrate temperature between 280 approximately 550°C with optimisation of reactor design and growth conditions. The gas phase prereaction is effectively restrained. These epilayers exhibit high crystallographic quality and reveal a mirror surface morphology. The peak halfwidths of X-ray diffraction patterns from their (400) faces are within 0.06 approximately 0.09°. The epilayers grown on (111) GaAs, (112¯0) Al2O3 and (100) Si have proven to be single crystalline feature. The optical and electrical characteristics of ZnS epilayers are measured by photoluminescence, cathodeluminescence, and the Van der Pauw method. The results indicate that there are not a large number of deep centers that could be detected both at 77K and at room temperature. A broad CL peak around 2.897eV and 2.672eV was observed only under very strong excitation. Their origin has not been examined. All epilayers present high resistivities up to 1013Ω&middotcm.

Low Temperature Growth of GaAs on Si byIon Beam Cluster Technique

Ion cluster beam (ICB) technique has many advantages in depositing thin film. In present study some characters of epitaxial layer of GaAs on Si by ICB have been investigated. these include: comparison of crystalline quality between ICB deposited GaAs and vacuum deposited GaAs, and to reveal defects by etching on GaAs-Si interface. The experimental results are discussed.

Diode-pumped passively Q-switched Nd:YVO_4 laser with GaAs saturable absorber

The intracavity photon density is assumed to be of Gaussian spatial distributions and its longitudinal variation is also considered in the rate equations for a laser diode (LD) end-pumped passively Q-switched Nd:YVO4 laser with GaAs saturable absorber. These space-dependent rate equations are solved numerically. The dependences of pulse width, pulse repetition rate, single-pulse energy, and peak power on incident pump power are obtained. In the experiment, the LD end-pumped passively Q-switched Nd:YVO4 laser with GaAs saturable absorber is realized and the experimental results are consistent with the numerical solutions.

Passive Q-switching of diode-pumped Yb:YAG microchip laser with ion-implanted GaAs

We reported a passive Q-switched diode laser pumped Yb: YAG microchip laser with an ion-implanted semi-insulating GaAs wafer. The wafer was implanted with 400-keV As+ in the concentration of 1016 ions/cm2. To decrease the non-saturable loss, we annealed the ion-implanted GaAs at 500℃ for 5 minutes and coated both sides of the ion-implanted GaAs with antireflection (AR) and high reflection (HR) films, respectively. Using GaAs wafer as an absorber and an output coupler, we obtained 52-ns pulse duration of single pulse.

Metamorphic In_(0.53)Ga_(0.47)As p-i-n photodetector grown on GaAs substrates by low-pressure MOCVD

Top-illuminated metamorphic In0.53Ga0.47As p-i-n photodetectors are grown on the ultrathin low- temperature InP buffered GaAs substrates. Photodetectors with the 300-nm-thick In0.53Ga0.47As absorption layer show a typical responsivity of 0.12 A/W to 1.55μm optical radiation, corresponding to an external quantum efficiency of 9.6%. Photodetectors with the active area of 50 × 50 （μm） exhibit the -3 dB bandwidth up to 6 GHz. These results are very encouraging for the application of this metamorphic technology to opto-electronic integrated circuit （OEIC） devices.

Terahertz emission by balanced nonlinear ef fects in air plasma

The evolution of terahertz （THz） waveform in air plasma driven by low-energy few-cycle laser pulses is investigated to improve the accuracy of the carrier envelope phase （CEP） determination. Based on the transient photocurrent model, a balanced spatial distribution of the Kerr and free-electron effects in the plasma is found at 109 μJ input energy. THz inversion occurs only once at the initial CEP of 0.5π, in which high-precision measurement of the CEP of few-cycle laser pulses is achieved.

Evaluation of four inch diameter VGF-Ge substrates used for manufacturing multi-junction solar cell

Low dislocation density Ge wafers grown by a vertical gradient freeze（VGF） method used for the fabrication of multi-junction photovoltaic cells（MJC） have been studied by a whole wafer scale measurement of the lattice parameter,X-ray rocking curves,etch pit density（EPD）,impurities concentration,minority carrier lifetime and residual stress.Impurity content in the VGF-Ge wafers,including that of B,is quite low although B_2O_3 encapsulation is used in the growth process.An obvious difference exists across the whole wafer regarding the distribution of etch pit density,lattice parameter,full width at half maximum（FWHM） of the X-ray rocking curve and residual stress measured by Raman spectra.These are in contrast to a reference Ge substrate wafer grown by the Cz method.The influence of the VGF-Ge substrate on the performance of the MJC is analyzed and evaluated by a comparison of the statistical results of cell parameters.

Heteroepitaxial growth of InP/GaAs(100) by metalorganic chemical vapor deposition

Using two-step method InP epilayers were grown on GaAs（100） substrates by low-pressure metalorganic chemical vapor deposition （LP-MOCVD）. X-ray diffraction （XRD） and room-temperature （RT） photolu- minescence （PL） were employed to characterize the quality of InP epilayer. The best scheme of growing InP/GaAs（100） heterostructures was obtained by optimizing the initial low-temperature （LT） InP growth conditions, investigating the effects of thermal cycle annealing （TCA） and strained layer superlattice （SLS） on InP epilayers. Compared with annealing, 10-periods Ga0.1In0.9P/InP SLS inserted into InP epilayers can improve the quality of epilayers dramatically, by this means, for 2.6-#m-thick heteroepitaxial InP, the full-widths at half-maximum （FWHMs） of XRD ω and ω-28 scans are 219 and 203 arcsec, respectively, the RT PL spectrum shows the band edge transition of InP, the FWHM is 42 meV. In addition, the successful growth of InP/In0.53Ga0.47As MQWs on GaAs（100） substrates indicates the quality of device demand of InP/GaAs heterostructures.

Compact all-optical switches based on photon-induced suppression of mode interference

An optically activated optical switch based on suppression of mode interference （SMI） is presented. The imaging properties of multi-mode interference （MMI） section in the switch with Y-branch can be modified by a controlling light injection. The switch was simulated by finite difference beam propagation method （FD-BPM） and fabricated on GaAlAs/GaAs epitaxial materials. At the wavelength of 1.31 μm, the primary experiment showed an extinction ratio of about 8 dB with controlling light power density of 73.5 W/mm^2.

Oxide-apertured VCSEL with short period superlattice

Novel distributed Bragg reflectors (DBRs) with 4.5 pairs of GaAs/AlAs short period superlattice (SPS) used in oxide-apertured vertical-cavity surface-emitting lasers (VCSELs) were designed. The structure of a 22-period Al0.9Ga0.1 As (69.5 nm)/4.5-pair [GaAs (10 nm)-AlAs (1.9 nm)] DBR was grown on an n+ GaAs substrate (100) 2° off toward <111>A by molecular beam epitaxy. The emitting wavelength was 850 nm with low threshold current of about 2 mA, corresponding to the threshold current density of 2 kA/cm2. The maximum output power was more than 1 mW. The VCSEL device temperature was increased by heating ambient temperature from 20 to 100℃ and the threshold current increased slowly with the increase of temperature.

1.3-μm uncooled 10 Gb/s directly modulated MQW AlGaInAs/InP laser diodes

In this paper, we report a novel 1.3-μm uncooled AlGaInAs/InP multiple quantum well （MQW） ridge waveguide laser diodes. By optimizing the design of MQW structure and facet coatings, together with the application of reversed-mesa ridge waveguide （RM-RWG） structure, polyimide planarization, and lift-off processes technology, an uncooled 1.3-μm, 10-Gb/s directly modulated MQW ridge waveguide laser diode was successfully fabricated. The threshold current and the slope efficiency were 7 mA and 0.48 mW/mA, respectively. The directly modulated bandwidths of 11 and 9.2 GHz were achieved at room temperature and 80℃, respectively.

Graded tensile-strained bulk InGaAs/InP superluminescent diode with very wide emission spectrum

A kind of novel broad-band superluminescent diodes (SLDs) using graded tensile-strained bulk InGaAs is developed. The graded tensile-strained bulk InGaAs is obtained by changing only group-Ⅲ trimethyl-gallium source flow during low-pressure metal organic vapor-phase epitaxy. At the injection current of 200 mA, the fabricated SLDs with such structure demonstrate full-width at half-maximum spectral width of 106 nm and the output light power of 13.6 mW, respectively.

High performance 1689-nm quantum well diode lasers

1689-nm diode lasers used in medical apparatus have been fabricated and characterized. The lasers had pnpn InP current confinement structure, and the active region consisted of 5 pairs of InGaAs quantum wells and InGaAsP barriers. Stripe width and cavity length of the laser were 1.8 and 300μm, respectively. After being cavity coated and transistor outline （TO） packaged, the lasers showed high performance in practice. The threshold current was about 13 ± 4 mA, the operation current and the lasing spectrum were about 58 ± 6 mA and 1689 ± 6 nm at 6-mW output power, respectively. Moreover, the maximum output power of the lasers was above 20 roW.

Room temperature continuous wave operation of 1.33-um InAs/GaAs quantum dot laser with high output power

Continuous wave operation of a semiconductor laser diode based on five stacks of InAs quantum dots （QDs） embedded within strained InGaAs quantum wells as an active region is demonstrated. At room temperature, 355-mW output power at ground state of 1.33-1.35 μm for a 20-μm ridge-waveguide laser without facet coating is achieved. By optimizing the molecular beam epitaxy （MBE） growth conditions, the QD density per layer is raised to 4 × 10^10 cm^-2. The laser keeps lasing at ground state until the temperature reaches 65 ℃.

Experimental study of mode characteristics for equilateral triangle semiconductor microcavities

Equilateral triangle semiconductor microcavities with tensile-strained InGaAsP multi-quantum-well as the active region are fabricated by the inductively coupled plasma (ICP) etching technique. The mode characteristics of the fabricated microcavities are investigated by photoluminescence, and enhanced peaks of the photoluminescence spectra corresponding to the fundamental transverse modes are observed for microcavities with side lengths of 5 and 10 um. The mode wavelength spacings measured experimentally coincide very well with those obtained by the theoretical formulae.