共查询到20条相似文献,搜索用时 31 毫秒
1.
Davis G.M. Zhang L. Chandler P.J. Townsend P.D. 《Photonics Technology Letters, IEEE》1993,5(4):430-432
The fabrication of planar optical waveguides in LiB3O 5 is discussed. Using 2-MeV 4He+ implantation with a dose of 1.5×1016 ions/cm2 at 300 K, the refractive indexes of a 0.2-μm-thick layer 5.1 μm below the crystal surface are reduced to form optical barrier guides. For this ion dose the maximum change from the bulk values of refractive index at a wavelength of 0.488 μm are 1.5%, 5.25%, and 4% for n x, n y, and n z, respectively. The refractive indexes of the guiding region change by less than 0.02% from the bulk values. The dose dependence of the optical barrier height has been measured. A threshold ion dose of about 0.75×1016 ions/cm2 is required to form a refractive index barrier and ion doses higher than about 2.5×1016 ions/cm2. saturate the refractive index decrease. Waveguide propagation losses for annealed single energy implants of dose 1.5×1016 ions/cm2 are dominated by tunneling and are estimated to be ~8.9 dB/cm for the z -cut waveguides used. Multiple energy implants broaden the optical barrier, and losses of <4 dB/cm have been observed 相似文献
2.
Maruyama A. Shen D.S. Chu V. Liu J.Z. Campbell I. Fauchet P.M. Wagner S. 《Electron Devices, IEEE Transactions on》1989,36(12):2853-2858
A detailed study of the growth of amorphous hydrogenated fluorinated silicon (a-Si:H, F) from a DC glow discharge in SiF4 and H2 is discussed. The electrical properties of the films can be varied over a very wide range. The bulk properties of the best films that were measured included an Urbach energy E u =43 meV, a deep-level defect density N s=1.5×1015 cm-3, and a hole drift mobility of 8×10-3 cm2 V-1 s-1, which reflects a characteristic valence band energy of 36 meV. It was found that E u, N s, and the density of surface states N ss are related to each other. Under the deposition condition of the films with the best bulk properties, N ss reaches its highest value of 1×1014 cm-2. It is suggested that in growth from SiF4/H2, the density of dangling bonds at the growing surface is very sensitive to the deposition conditions 相似文献
3.
The magnitudes of linear electrooptic coefficients r 13 and r 33 in Zn:LiTaO3 repoled channel waveguides are reported. The measurements were made at 0.633-μm wavelength using a Fabry-Perot interferometer. The waveguides were produced by diffusion from the vapor phase at a temperature above the Curie temperature. For full recovery of the Pockels effect, an electric field of 200 V/cm is needed during repoling. The measured values of r 13 and r 33 at 32-MHz modulation frequency are 7.2 and 30.3 pm/V, respectively. The difference between unclamped and clamped coefficients is comparable to that from bulk crystals. Measurements were also made on Ti:LiNbO3 waveguides that did not require repoling, and good agreement with bulk crystal values was obtained 相似文献
4.
de Murcia M. Gasquet D. Elamri A. Nougier J.-P. Vanbremeersch J. 《Electron Devices, IEEE Transactions on》1991,38(11):2531-2539
The variation of the diffusion coefficient D (E ) versus the electric field strength E is determined at 300 K in n-type GaAs (N D=3×10-17 cm-3 ), using pulsed high-frequency noise measurements. D (E ) is found to increase slightly at low field, then to decrease down to one tenth of its ohmic value near the threshold field. Long (⩾4 μm) real n+-n-n+ Gunn diodes, with an arbitrary doping profile, can be modeled. Comparisons are made, and excellent agreement is found, between experimental and theoretical characteristics of two real diodes, with notch and with gradual doping profiles. The doping profile N D(x ) is shown to have a considerable influence on the diode behavior, in regard to the electric field profile as well as the noise characteristics. Using the impedance field method, the noise current is modeled and found to by very sensitive in the D (E ) variation law, in particular in the range of 2.5-4 kV/cm. The agreement between the experimental noise and the computed noise of real diodes is quite satisfactory when using the D (E ) determined 相似文献
5.
Miliou A. Zhenguang H. Cheng H.C. Srivastava R. Ramaswamy R.V. 《Quantum Electronics, IEEE Journal of》1989,25(8):1889-1897
A systematic study of waveguides fabricated by K+-Na + exchange in soda-lime silicate and BK7 glasses is presented. The measured K+ concentration profile, the refractive index profile, and the diffusion profile obtained by solving the one-dimensional diffusion equation are correlated to explain the differences in the index profiles in the two glasses. The mobility of the potassium ions was measured by fabricating waveguides using electromigration. Surface waveguides formed by diffusion from a molten KNO3 salt bath were buried by applying an electric field. Single-mode channel waveguides for operation at a wavelength of 1.3 μm that exhibit excellent mode matching with conventional optical fibers, achieving a fiber-waveguide insertion loss of less than 1 dB for a 20-mm-long waveguide, have been obtained 相似文献
6.
Planar optical waveguides in z -cut LiNbO3 fabricated by the annealed proton-exchange technique using pure pyrophosphoric acid as the initial proton source have been investigated. A generalized Gaussian function was used to accurately model the refractive-index profile, resulting in considerable improvements over previous work. The nonlinear dependence of the index on the proton concentration was verified by directly calculating the change in the area under the index versus depth curves. Annealing was found to allow for flexibility in the tailoring of the waveguide parameters. An empirical correlation of the changes in these parameters with the fabrication conditions was achieved through the use of a general power law 相似文献
7.
A thorough and detailed characterization of annealed proton-exchanged (APE) waveguides in Z -cut LiNbO3 is described. The mode index measurements in planar waveguides as a function of wavelength and annealing time are reported, including useful analytical relations for the refractive index change, its dispersion, and the depth profile as a function of annealing parameters. Analytical expressions for the mode propagation characteristics are presented and experimentally verified with reasonable accuracy. It is shown that the planar waveguide characterization results can be used to model the channel waveguide characteristics accurately. The model provides closed-form expressions for the mode index and the mode field profile, and the theoretical results are in excellent agreement with the measured data. The technique is used to accurately predict the phase mismatch between the fundamental and second harmonic modes in frequency-doubling experiments using APE channel waveguides. An optimum waveguide geometry for which the phase mismatch is relatively insensitive to the waveguide nonuniformity was predicted and verified experimentally 相似文献
8.
p+-n junction diodes for sub-0.25-μm CMOS circuits were fabricated using focused ion beam (FIB) Ga implantation into n-Si (100) substrates with background doping of Nb=(5-10)×10 15 and Nb+=(1-10)×1017 cm-3. Implant energy was varied from 2 to 50 keV at doses ranging from 1×1013 to 1×1015 cm-2 with different scan speeds. Rapid thermal annealing (RTA) was performed at either 600 °C or 700°C for 30 s. Diodes fabricated on Nb+ with 10-keV Ga+ exhibited a leakage current (IR) 100× smaller than those fabricated with 50-keV Ga+. Tunneling was determined to be the major current transport mechanism for the diodes fabricated on Nb+ substrates. An optimal condition for I R on Nb+ substrates was obtained at 15 keV/1×1015 cm-2. Diodes annealed at 600°C were found to have an I R 1000× smaller than those annealed at 700°C. I -V characteristics of diodes fabricated on Nb substrates with low-energy Ga+ showed no implant energy dependence. I -V characteristics were also measured as a function of temperature from 25 to 200°C. For diodes implanted with 15-keV Ga +, the cross-over temperatures between I diff and I g-r occurred at 106°C for Nb + and at 91°C for Nb substrates 相似文献
9.
AlGaAs/GaAs collector-up heterojunction bipolar transistors (HBTs) with a heavily carbon-doped base layer were fabricated using oxygen-ion implantation and zinc diffusion. The high resistivity of the oxygen-ion-implanted AlGaAs layer in the external emitter region effectively suppressed electron injection from the emitter, allowing collector current densities to reach values above 105 A/cm 2. For a transistor with a 2-μm×10-μm collector, f T was 70 GHz and f max was as high as 128 GHz. It was demonstrated by on-wafer measurements that the first power performance of collector-up HBTs resulted in a maximum power-added efficiency of as high as 63.4% at 3 GHz 相似文献
10.
Ashley P.R. Chang W.S.C. Buchal C.J. Thomas D.K. 《Lightwave Technology, Journal of》1989,7(5):855-862
Electrooptic modulators in Ti-ion-implanted LiNbO3 waveguides are discussed. Low loss (<1-dB/cm) planar and channel waveguides were fabricated and compared to indiffused waveguides. Higher Δn values are obtained, allowing smaller waveguide geometries and tighter mode confinement. Wavelengths of 0.85 and 1.3 μm are used. The small mode profiles resulting from the Ti doses up to 4×1017 Ti/cm2 resulted in V -L products of 8.8 V-mm at 0.85 μm and 20 V-mm at 1.3 μm. These values are lower than any previously reported for a Mach-Zehnder modulator using a buffer layer. Comparison of diffused and implanted waveguide modulators indicated that modular efficiency can be optimized by electrode gap spacing and enhanced with smaller mode profiles achievable in implanted guides 相似文献
11.
《Electron Devices, IEEE Transactions on》1990,37(1):153-158
The fabrication of a silicon heterojunction microwave bipolar transistor with an n+ a-Si:H emitter is discussed, and experimental results are given. The device provides a base sheet resistance of 2 kΩ/□ a base width 0.1 μm, a maximum current gain of 21 (V CE=6 V, I c=15 mA), and an emitter Gummel number G E of about 1.4×1014 Scm-4. From the measured S parameters, a cutoff frequency f t of 5.5 GHz and maximum oscillating frequency f max of 7.5 GHz at V CE=10 V, I c=10 mA are obtained 相似文献
12.
Peransin J.-M. Vignaud P. Rigaud D. Vandamme L.K.J. 《Electron Devices, IEEE Transactions on》1990,37(10):2250-2253
The 1/f noise in normally-on MODFETs biased at low drain voltages is investigated. The experimentally observed relative noise in the drain current S I/I 2 versus the effective gate voltage V G=V GS-V off shows three regions which are explained. The observed dependencies are S I/I 2∝V G m with the exponents m =-1, -3, 0 with increasing values of V G. The model explains m =-1 as the region where the resistance and the 1/f noise stem from the 2-D electron gas under the gate electrode; the region with m =0 at large V G or V GS≅0 is due to the dominant contribution of the series resistance. In the region at intermediate V G , m =-3, the 1/f noise stems from the channel under the gate electrode, and the drain-source resistance is already dominated by the series resistance 相似文献
13.
Rapid isothermal processing of strained GeSi layers 总被引:1,自引:0,他引:1
《Electron Devices, IEEE Transactions on》1992,39(1):56-63
A cold-wall rapid thermal processor was used to study the oxidation and annealing properties of GexSi1-x strained layers. The dry oxidation rate of GexSi1-x was found to be the same as that of Si, while the wet oxidation rate was found to be higher than that of Si, and the oxidation rate increases with the Ge concentration (up to 20% in this study). A high fixed oxide charge density (>5×1011 /cm2) and interface trap level density (>1012 /cm2-eV) at the oxide interface have been determined from capacitance-voltage measurements. Using techniques such as X-ray rocking curve analysis and I -V and C -V measurements of the p-n heterojunction it was found that the degradation of electronic properties of metastable GexSi1-x strained layers during rapid thermal annealing are related to the formation of structural defects at the heterointerfaces 相似文献
14.
Yiqi Zhuang Qing Sun 《Electron Devices, IEEE Transactions on》1991,38(11):2540-2547
Accelerated life tests with high-temperature storage and electric aging for n+-p-n silicon planar transistors were carried out. Current gain h FE increases monotonously with time during the tests, and the h FE drift is correlated with initial measured 1/f noise in the transistors, i.e. the drift amount significantly increases with the increase of noise level. The correlation coefficient of relative drift Δh FE /h FE and 1/f noise spectral density S iB(f ) is far larger than that of Δ h FE/h FE and initial DC parameters of the transistors. A quantitative theory model for the h FE drift has been developed and explains the h FE drift behavior in the tests, which suggests that the h FE drift and 1/f noise can be attributed to the same physical origin, and both are caused by the modulation of the oxide traps near the Si-SiO2 interface to Si surface recombination. 1/f noise measurement, therefore, may be used as a fast and nondestructive means to predict the long-term instability in bipolar transistors 相似文献
15.
The electrical properties of MOS capacitors with an indium tin oxide (ITO) gate are studied in terms of the number density of the fixed oxide charge and of the interface traps N f and N it, respectively. Both depend on the deposition conditions of ITO and the subsequent annealing procedures. The fixed oxide charge and the interface-trap density are minimized by depositing at a substrate temperature of 240°C at low power conditions and in an oxygen-rich ambient. Under these conditions, as-deposited ITO films are electrically conductive. The most effective annealing procedure consists of a two-step anneal: a 45-s rapid thermal anneal at 950°C in N2, followed by a 30 min anneal in N2/20% H2 at 450°C. Typical values obtained for N it and N f are 4.2×1010 cm-2 and 2.8×1010 cm-2, respectively. These values are further reduced to 1.9×1010 cm-2 and ≲5×109 cm-2, respectively, by depositing approximately 25 nm polycrystalline silicon on the gate insulation prior to the deposition of ITO 相似文献
16.
An In0.41Al0.59As/n+-In0.65 Ga0.35As HFET on InP was designed and fabricated, using the following methodology to enhance device breakdown: a quantum-well channel to introduce electron quantization and increase the effective channel bandgap, a strained In0.41Al0.59As insulator, and the elimination of parasitic mesa-sidewall gate leakage. The In0.65Ga0.35As channel is optimally doped to N D=6×1018 cm-3. The resulting device (L g=1.9 μm, W g =200 μm) has f t=14.9 GHz, f max in the range of 85 to 101 GHz, MSG=17.6 dB at 12 GHz V B=12.8 V, and I D(max)=302 mA/mm. This structure offers the promise of high-voltage applications at high frequencies on InP 相似文献
17.
The carrier-induced index change was measured using a novel injection-reflection technique in combination with differential carrier lifetime data. The observed relation between index change and injected carrier density at bandgap wavelength is nonlinear and is approximately given by δn act=-6.1×10-14 ( N )0.66 for a 1.5-μm laser and δn act=-1.3×10-14 (N )0.68 for a 1.3-μm laser. The carrier-induced index change for a 1.3-μm laser at 1.53-μm wavelength is smaller and is given by δn act=-9.2×10-16 (N )0.72 相似文献
18.
Tachikawa K. Togano K. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1989,77(8):1124-1131
Studies of practical properties, such as upper critical field (H C2) and critical-current density, of high-T c oxide superconductors of Y-Ba-Cu-O Bi-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O systems are reviewed. The Hc2 of these materials is much higher than that of conventional metallic superconductors, indicating a high potential for practical applications, even when they are used in liquid nitrogen. However, the HC2 of these materials is also highly anisotropic, as can be expected from an examination of their crystal structure. In addition to this anisotropy, the presence of weak links and a weak pinning force in this material limit the transport current density J 3 to much lower levels than that required for practical applications. Recent fabrication processes that have good potential for producing wire or tape conductors or high-T c oxide are reviewed. Some details are presented of the powder method and other fabrication processes using diffusion, solidification, and deposition techniques. For the Ag-sheathed oxide tapes, J c values exceeding 10000 A/cm2 at 77 K and 0 T have been reported for both Bi and Tl oxide materials 相似文献
19.
The development of incremental and decremental V T extractors based on the square-law characteristic and an n ×n 2 transistor array is described. Different implementations have been discussed and the effect of nonidealities such as mobility reduction, channel-length modulation, mismatch, and body effect has been analyzed. Besides automatic V T extraction, parameter K of an MOS transistor can also be extracted automatically using the V T extractor, without any need of calculation and delay, and the extracted V T and K are, respectively, in voltage and current. Experimental results are presented and indicate that the differences between extracted values using the V T extractor and the most popular numerical method are as small as 0.15% and 0.064%. Additional applications, such as in level shifting, temperature compensation, and temperature measurement, where the V T extractor can be used either as a PTAT sensor or as a centigrade sensor, are presented 相似文献
20.
Minority-carrier electron lifetime, mobility and diffusion length in heavily doped p-type Si were measured at 296 and 77 K. It was found that a 296 K μn (pSi)≈μn (nSi) for N AA≲5×1018 cm-3, while μn (pSi)/μn (nSi)≈1 to 2.7 for higher dopings. The results also show that for N AA≲3×1019 cm-3, D (pSi) at 77 K is smaller than that at 296 K, while for higher dopings D n (pSi) is larger at 77 K than at 296 K. μn (pSi) at 77 K increases with the increasing doping above N AA>3×1018 cm-3, in contrast to the opposite dependence for μn (nSi) in n+ Si 相似文献