一种激光二极管像散光束准直整形方法研究

为了准直并整形具有像散的激光二极管光束,采用高斯光束q参量变换规律,推导了利用柱面自聚焦透镜整形激光二极管光束应满足的条件,并在此基础上,通过软件模拟优化,得到了一套效果良好的光束整形准直系统。经过准直整形后光束快慢轴方向发散角基本相等,均小于0.7mrad,束腰位置差异小于2.8mm。结果表明,系统中柱面自聚焦透镜的应用起到了较好的效果,准直整形后的光束具有发散角较小且旋转对称等特点。     

A study of chemical beam epitaxy of GaAs using tris-dimethylaminoarsenic

The growth of GaAs by chemical beam epitaxy using triethylgallium and trisdimethylaminoarsenic has been studied. Reflection high-energy electron diffraction (RHEED) measurements were used to investigate the growth behavior of GaAs over a wide temperature range of 300–550°C. Both group III- and group Vinduced RHEED intensity oscillations were observed, and actual V/III incorporation ratios on the substrate surface were established. Thick GaAs epitaxial layers (2–3 μm) were grown at different substrate temperatures and V/III ratios, and were characterized by the standard van der Pauw-Hall effect measurement and secondary ion mass spectroscopy analysis. The samples grown at substrate temperatures above 490°C showed n-type conduction, while those grown at substrate temperatures below 480°C showed p-type conduction. At a substrate temperature between 490 and 510°C and a V/III ratio of about 1.6, the unintentional doping concentration is n ∼2 × 10¹⁵ cm⁻³ with an electron mobility of 5700 cm²/V·s at 300K and 40000 cm²/V·s at 77K.     

Reduction of dislocations in GaAs and InP epitaxial layers by quasi ternary growth and its effect on device performance

It is shown that strained isoelectronically doped buffer layers grown on GaAs and InP substrates allow one to reduce the dislocation density as well as the deep level concentration. Photoluminescence measurements show an improved near gap luminescence and a reduced deep level emission. This has been also confirmed by DLTS measurements. The higher material quality is also reflected in the device performance. GaAs Schottky diodes (n ˜0.5 · 10¹⁶Cm^-3) exhibit a leakage current of 100 pA up to 50 V reverse bias at room temperature even with large Schottky contact area of 125 μm × 60 μm. This technique allows the quality of electronic and optoelectronic devices to be improved.     

Fabrication and Characterization of Silicon Microchannel Plates as Temperature-Sensing Materials

Silicon microchannel plates (Si MCPs) are prepared by photo-assisted electrochemical etching (PAECE), and their temperature-sensing behavior based on the Seebeck effect is studied. In particular, the dependence of the temperature sensitivity on the orientation and pore size of the Si MCPs is determined in detail. Our results clarify the relationship between the temperature sensitivity and orientation of the Si MCPs. When the angle between the measured orientation and edge of the square micropore is 45°, the samples with pore dimensions of 5 μm × 5 μm and 3 μm × 3 μm show temperature sensitivities of 1.88 mV/°C and 0.93 mV/°C, respectively. In general, the sample with pore size of 5 μm × 5 μm exhibits higher sensitivity. Si MCPs which are compatible with integrated circuit (IC) processing have promising applications in integrated microtemperature sensing.     

Growth of device quality GaAs by chemical beam epitaxy

The growth of high purity GaAS with excellent uniformity and very low defect density by chemical beam epitaxy using triethylgallium and arsine is described. The residual background impurity is mostly carbon. A mobility of 518 cm²/Vs with a hole density of 3.6 x 10¹⁴ cm⁻³ has been obtained for a growth temperature of 500° C. The electrical quality is further evaluated by fabricating a Si doped epilayer into MESFET device using 1 μm gate length. A transconductance of 177 mS/mm has been measured. The results indicate that chemical beam epitaxy is a very attractive growth technique for GaAs integrated circuits.     

Optimization and Fabrication of a Thick Printed Thermoelectric Device

Thermoelectric power generation technology aims to convert thermal energy into electricity. Micromodule design optimization depends directly on the thermal environment. For low thermal energy input, optimized thermoelectric devices require 100 μm to 500 μm element thickness. These dimensions currently present a challenge for standard mass-production manufacturing techniques. In this paper, a unique printing technology for micromodule fabrication is presented. This technology is compared with a traditional bulk thermoelectric manufacturing process to highlight the advantages of the printing process to obtain scalable thermoelectric devices. Initial thermoelectric materials have been integrated in inks and then deposited by a spray technology onto a polymer substrate. A complete micromodule for application on nonplanar surfaces is also presented.     

Simulation Design of Collimation Zoom Optical System Based on Laser Ranging

Laser ranging is a crucial issue for collimation zoom optical systems, in order to make sure the beam alignment adapt to the aperture, the spatial divergence angle of the laser beam should be improved. In this paper, a collimation zoom optical system was designed based on the principle of non-focal magnification collimation and direct beam expansion. The optimized operation function DMVA is input into the Zemax simulation system to control the image height, and the curvature, thickness and air space of each lens of the system are optimized to reach the index requirements. The results of the optical track simulation shows that the energy distribution is uniform and non-dispersive. The collimation zoom system, four-group telescope is used instead of the group telescope structure, which have simple structure, the design of cam curve ensure the boresight of optical axes meets the design index, that reduce the ranging error efficiently. The accuracy error of the instrument is less then 0.5 m when field ranging is 10 km.     

Analysis of fiber lens with gradient index based on thin lens equivalence

Optical communication components have been devel-oped currentlytowards the direction of micromation andintegration. The problem which li mits the componentperformancesis howto couple the function slugs to theinput-output fiber effectively,as appeared in a…     

Ion-assisted molecular beam epitaxy of GaAs on Si(100)

GaAs was grown by molecular beam epitaxy (MBE) and ion-assisted MBE on Si(100) substrates. Three-dimensional (3D) island nucleation, observed during MBE growth, was eliminated during ion-assisted MBE when the ion energyE was >25 eV and the product ofE and the current densityJ was ≈6-12 eV mA/cm². IncreasingEJ to ≈15 eV mA/ cm² resulted in excessive ion damage. Decreasing the substrate temperature from 280 to 580° C during ion-assisted MBE yielded a slight decrease in surface roughness, and flatter surfaces were obtained for lower As⁴/Ga flux ratios. The suppression of 3D island nucleation led to an improvement in the crystalline perfection of thicker GaAs films. For example, the x-ray diffraction rocking-curve full-width-at-half-maximum values for 0.5 μm thick films grown at 380° C decreased from 1700 arcsec to 1350 arcsec when ion irradiation was used during nucleation. IAMBE allowed nucleation of thin, relatively flat-surfaced GaAs films even at 580° C, resulting in FWHM values of 1850 arcsec for 0.14 /μm thick films.     

MBE growth and characteristics of periodic index separate confinement heterostructure InGaAs quantum-well lasers

We have used solid-source molecular beam epitaxy (MBE) to grow InGaAs quantum-well lasers emitting at 980nm in a novel configuration of periodic index separate confinement heterostructure (PINSCH). Periodic multilayers (GaAs/AlGaAs) are utilized as optical confinement layers to reduce the transverse beam divergence as well as to increase the maximum output power. The multilayers are grown by temperature modulation MBE without any shutter operation. The heterointerfaces in the multilayers are linearly graded such that the energy barrier heights are greatly decreased. This has led to a drastic reduction in the series resistance which is essential in the performance of high output power. The 5μm × 750μm device has far-field angles of 10° by 20°, a threshold current of 45 mA, an external differential quantum efficiency of 1.15 mW/mA (90%), and an output power of 620 mW, all measured at room temperature under CW operation. A record high fiber coupling efficiency of 51% has been achieved and more than 130 mW of power is coupled into a 5μm-core single mode fiber.     

Mosfet fabrication using ion beam nitridation

Ion beam nitridation has been suggested as an alternative to the conventional local oxidation process which is used in the fabrication of most metal-oxide-semiconductor (MOS) integrated circuits. The implantation of 2 keV nitrogen ions in doses of up to 8 x 10¹⁷ cm^-2 results in the formation of a silicon nitride layer approximately 10 nm thick. Herein we describe the electrical characteristics of n-channel silicon gate metal-oxide-semiconductor-field-effect-transistors (MOSFETs) fabricated using this modified local oxidation process, and compare them to devices fabricated simultaneously but using the conventional local oxidation technology. The effective device channel lengths and widths are determined from the electrical characteristics of devices with mask (ideal) dimensions of 4, 6, 8 or 10 μm. The ion beam nitrided devices exhibit a significant reduction in the lateral oxidation effect. A 1.3 μm increase in channel width relative to conventional processing is observed for the ion beam nitrided devices with a 690 mm thick field oxide. On the other hand, fixed oxide charge densities are found to increase by a factor of about two due to the nitrogen implantation, and device channel mobilities are reduced by about 25%.     

Effect of substrate temperature on aligned high-density carbon nanotubes deposited by RF-PECVD

The high-density carbon nanotubes (CNTs) are synthesized on Fe/Si substrate in the mixture of acetylene and hydrogen gas by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) method. The effects of substrate temperature on the growth of CNTs are studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The quality of CNTs is improved considerably by increasing the substrate temperature while the beam density is increased and graphitization degree (ID/IG) is enhanced. The best aligned CNTs are prepared at 750 oC, the beam density is about 1.6 × 103/μm2, and ID/IG is about 0.93. Temperature influence is also discussed.     

Silicon epitaxial growth using dichlorosilane

This paper describes the results obtained growing silicon epitaxial structures in a horizontal reactor using dichlorosilane as the silicon source material. The growth rate dependence upon temperature and dichlorosilane flux has been obtained for rates ranging from 1 μm/min to 20 μm/min for all major crystal orientations. Characterization was carried out using spreading resistance measurements, IR interference, preferential etching, and optical microscopy, for layer thicknesses ranging from 3 μm to 250 μm. The majority of the structures grown were multi-layered, intended for use in fabricating high voltage power transistors. Controlled doping levels over the range 5 × 10¹³ to 1 × 10¹⁷ were obtained using either AsH³ or B²Hg⁶ as the dopant source. The effect of growth parameters on the doping profile and quality of such layers is described. Operating devices fabricated from this material exhibit bulk avalanche breakdown voltage. Large area npn transistors with collector base voltages greater than 2000 volts and current gains of 10 to 30 have also been fabricated.     

Selective etch-back and growth of InGaAs ON (100) Fe:lnP by electroepitaxy

Selective etch-back prior to growth of InGaAs islands on SiO₂-masked (100)Fe-doped InP substrates was performed by electroepitaxy. The etch-back of the substrate and the growth of the layer was done at a constant furnace temperature of 640° C by passing a direct electric current from the melt to the substrate for etch-back and from the substrate to the melt for growth. The current density used was 1 to 20 A/cm² for a period from 15 to 60 min. The isolated InP regions were of various sizes (40 × 1000μm to 3000 × 3000μm), and different geometries (narrow and wide strips, square, circular). A uniform etch-back and uniform growth with excellent surface morphology was obtained on strips as wide as 200μm and on circles withd < 500μm. For islands with wider geometry, growth as well as etch-back were uniform up to 100–200μm from the periphery with excellent surface morphology. The etch-back and growth profiles are trapezoid-shaped and are not influenced by the difference in chemical activity between crystalline planes. The orientation dependence of the etch rate was {110} > {100} > {011} > {111} B > {111} A.     

Excimer laser-assisted planarization of thick diamond films

The planarization of polycrystalline diamond films is critical for a large number of industrial applications. We have investigated a laser-assisted method for planarization of thick diamond films. This method is based on the application of excimer laser combined with simultaneous rotation of the sample. Thick diamond films (average surface roughness: ∼20 μm and thickness ∼500 μm) were fabricated by plasma jet chemical vapor deposition process. The planarization of diamond films was found to be critically dependent on the angle of incidence of laser beam. Smoother surfaces were obtained at higher incidence angles (θ = 80°). However, by combination of sample rotation with laser irradiation at higher incidence angles (θ = 80°), maximum surface planarization was achieved. Under optimum conditions, the surface roughness of the samples were reduced from 20 to 0.1 μm. The mechanisms for surface planarization of thick diamond films are discussed.     

Comparative study of electrically conductive thick films with and without glass

An air-fireable, glass-free, electrically conductive thick-film material (96.6% Ag, 1.38% Cu, 0.28% Al, 0.35% Ti, and 1.39% Sn by weight) and a conventional glass-containing, electrically conductive thick-film materials (96.6% Ag and 3.4% glass frit by weight), both on alumina substrates, were studied by electrical, mechanical, thermal, and microscopic methods. The volume electrical resistivity of the glass-free thick film (2.5×10⁻⁶ Ω·cm, 30-μm thick) is lower than that of the glass-containing thick film (3.9×10⁻⁶ Ω·cm, 19-μm thick), with each film processed at its optimum firing temperature. The optimum firing temperature is 930°C and 850°C for glass-free and glass-containing thick films, respectively, as indicated by the criteria of low resistivity and high scratch resistance. The glass-free thick film has a higher scratch resistance than the glass-containing thick film, both fired at their respective optimum temperatures, suggesting that the former has higher bond strength to the alumina substrate. The formation process of the glass-free and glass-containing thick films is similar. The process involves solid-state diffusion of silver, which results in a silver network and grain boundaries. However, the sintering of silver particulates in the glass-containing thick film is enhanced by the viscous flow of glass.     

光通信中高精度激光束准直系统优化设计

基于空间解析几何与矢量形式的折射定理为基础,研究了非球面、非轴对称的激光束准直光学系统,并对空间光线的传输进行了严格的理论推导,得出了光束发散角的传递矩阵递推公式,并对激光束的发散角进行了优化设计.利用激光束质量诊断仪对准直系统的发散角进行了实验测试,结果表明准直系统能达到较高的准直精度.本设计方法能广泛应用于复杂的非球面光学系统设计中.     

The growth of GaAs,AIGaAs, InP and InGaAs by chemical beam epitaxy using group III and V alkyls

The growth kinetics of chemical beam epitaxy (CBE) were investigated with the growth of GaAs, AIGaAs, InP, and InGaAs. Results obtained with epilayers grown by using trimethylarsine (TMAs) and triethylphosphine (TEP) instead of arsine (AsH3) and phosphine (PH₃) were reviewed with some additional results. The CBE grown epilayers have similar optical quality to those grown by molecular beam epitaxy (MBE). Superlattices of GaAs/AlGaAs with abrupt interfaces have been prepared. Since trimethylindium (TMIn) and triethylgallium (TEGa) used in the growth of InGaAs emerged as a single mixed beam, spatial composition uniformity was automatically achieved without the need of substrate rotation in the InGaAs epilayers grown. Lattice-mismatch Δα/α< 1 x 10^-3 have been reproducibly obtained. For epilayers grown with high purity TMAs source, room-temperature electron mobility as high as 9000 cm²/V sec and concentrations of ˜7 x 10¹⁵ cm^-3 were produced. In general, the electron mobilities were as good as those obtained from low-pressure metalorganic chemical vapor deposition. (MO-CVD). Unlike MBE, since the In and Ga were derived by the pyrolysis of TMIn and TEGa molecules at the heated substrate surface, respectively, oval defects observed in MBE grown epilayers due to Ga splitting from Ga melt were not present in CBE grown epilayers. This is important for integrated circuit applications. Unlike MO-CVD, the beam nature of CBE allows for selective area growth of epilayers with well-defined smooth edges using mask shadowing techniques. Typically, growth rates of 2-5μm/h for InP, 2-6μm/h for GaAs and AIGaAs, and 2-5μm/h for InGaAs were used.     

Molecular beam epitaxial growth and performance of integrated two-color HgCdTe detectors operating in the mid-wave infrared band

The first report of molecular beam epitaxial growth and performance of HgCdTe two-color detectors for the simultaneous detection of radiation at 4.1 and 4.5 μm is presented. In-situ doped devices with the n-p-n architecture were grown by molecular beam epitaxy on (211)B CdZnTe substrates. Representative structures exhibited x-ray rocking curves with full width at half-maxima of 40–60 arcs. The typical near surface etch pit density in these structures were 4−7 × 10⁶ cm⁻². The devices were processed as mesa diodes and electrical contacts were made to the two n-type layers and the p-type layer to facilitate simultaneous operation of the two p-n junctions. The spectral response characteristics of the devices were characterized by sharp turn-on and turn-off for both bands, with R₀A values >5 × 10⁵ ωcm² at 77K. The detectors exhibited quantum efficiencies >70% in both bands.     

Integration of microdiffractive lens with continuous relief withvertical-cavity surface-emitting lasers using focused ion beam directmilling

A novel one-step integration of bottom-emitting vertical-cavity surface-emitting laser (VCSEL) (operation wavelength of 980 nm) with microdiffractive lens by means of focused ion beam (FIB) technology is described. A diffractive lens with continuous relief, diameter of 140 μm, and six annulus was designed and fabricated using FIB direct milling on the backside of VCSEL with GaAs substrate for beam collimation. The divergence angle (half angle) of the VCSEL was reduced from 12° before integration of the VCSEL/diffractive optical elements (DOEs) to 0.6° after FIB integration, allowing for an interconnect length of ~4 mm. It was proven by device testing that there is little influence upon the VCSEL performance after FIB processing