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1.
Experimental results are presented for SiC epitaxial layer growths employing a unique planetary SiC-VPE reactor. The high-throughput, multi-wafer (7×2″) reactor, was designed for atmospheric and reduced pressure operation at temperatures up to and exceeding 1600°C. Specular epitaxial layers have been grown in the reactor at growth rates ranging from 3–5 μm/h. The thickest layer grown to date is 42 μm thick. The layers exhibit minimum unintentional n-type doping of 1×10 15 cm −3, and room temperature mobilities of 1000 cm 2/V s. Intentional n-type doping from 5×10 15 cm −3 to >1×10 19 cm −3 has been achieved. Intrawafer layer thickness and doping uniformities (standard deviation/mean at 1×10 16 cm −3) are typically 4 and 7%, respectively, on 35 mm diameter substrates. Moderately doped, 4×10 17 cm −3, layers, exhibit 3% doping uniformity. Recently, 3% thickness and 10% doping uniformity (at 1×10 16 cm −3) has been demonstrated on 50 mm substrates. Within a run, wafer-to-wafer thickness deviation averages 9%. Doping variation, initially ranging as much as a factor of two from the highest to the lowest doped wafer, has been reduced to 13% at 1×10 16 cm −3, by reducing susceptor temperature nonuniformity and eliminating exposed susceptor graphite. Ongoing developments intended to further improve layer uniformity and run-to-run reproducibility, are also presented. 相似文献
2.
In this paper, we will discuss how the unique growth chemistry of MOMBE can be used to produce high speed GaAs/AlGaAs heterojunction bipolar transistors (HBTs). The ability to grow heavily doped, well-confined layers with carbon doping from trimethylgallium (TMG) is a significant advantage for this device. However, in addition to high p-type doping, high n-type doping is also required. While elemental Sn can be used to achieve doping levels up to 1.5×10 19 cm -3, severe segregation limits its use to surface contact layers. With tetraethyltin (TESn), however, segregation does not occur and Sn doping can be used throughout the device. Using these sources along with triethylgallium (TEG), trimethylamine alane (TMAA), and AsH 3, we have fabricated Npn devices with 2 μm×10 μm emitter stripes which show gains of ≥ 20 with either ƒ t = 55 GHz and ƒ max = 70 GHz or ƒ t = 70 GHz and ƒ max = 50 GHz, depending upon the structure. These are among the best RF values reported for carbon doped HBTs grown by any method, and are the first reported for an all-gas source MOMBE process. In addition, we have fabricated a 70 transistor decision circuit whose performance at 10 Gb/s equals or exceeds that of similar circuits made from other device technologies and growth methods. These are the first integrated circuits reported from MOMBE grown material. 相似文献
3.
The effect of oxide impurity on the physical properties of 62ZrF 4---8LaF 3---30BaF 2 (mol.%) glass was studied by equimolecular substitution of BaO for BaF 2. It is shown that the oxide impurity decreases the infrared transparency beyond 6 μm, shifts the transmission cut-off wavelength to higher frequencies and causes an additional absorption shoulder at 1350 cm −1. The oxide impurity also increases the glass transition temperature, the crystallization temperature and the viscosity of the melt. The additional infrared absorption of oxide impurity in the fluorozirconate glasses results from the multiphonon process of the vibration of F---Zr---O bonds at 680 cm −1. 相似文献
4.
New multicomponent PbF 2–InF 3–GaF 3 bulk glasses have been investigated. They show lower phonon energy (540 cm −1) in comparison with 580 cm −1 for ZBLAN. Large PbF 2 concentration provided glasses with high refractive index up to 1.582 and the viscosity curves revealed an excellent thermal compatibility with ZBLAYN glass. A multimode fiber with a numerical aperture of 0.51, a loss of 0.85 dB/m at 1.3 μm was fabricated using the rotational casting method. 相似文献
5.
Thermally stimulated luminescence (TSL) and infrared (IR) spectroscopy were measured in plasma grown Si 1−xGe xO 2 ( x=0, 0.08, 0.15, 0.25, 0.5) with different thicknesses (12–40 nm). A comparison with the TSL properties of thermally grown SiO 2 and GeO 2 was also performed. A main IR absorption structure was detected, due to the superposition of the peaks related to the asymmetric O stretching modes of (i) Si–O–Si (at ≈1060 cm −1) and (ii) Si–O–Ge (at 1001 cm −1). Another peak at ≈860 cm −1 was observed only for Ge concentrations, x>0.15, corresponding to the asymmetric O stretching mode in Ge–O–Ge bonds. A TSL peak was observed at 70°C, and a smaller structure at around 200°C. The 70°C peak was more intense in all Ge rich layers than in plasma grown SiO 2. Based on the thickness dependence of the signal intensity we propose that at Ge concentrations 0.25 x0.5 TSL active defects are localised at interfacial regions (oxide/semiconductor, Ge poor/Ge rich internal interface, oxide external surface/atmosphere). Based on similarities between TSL glow curves in plasma grown Si 1−xGe xO 2, thermally grown GeO 2 and SiO 2 we propose that oxygen vacancy related defects are trapping states in Si 1−xGe xO 2 and GeO 2. 相似文献
6.
We have grown layers of Ga 1−xIn xAs:C ( x ≈ 0.01) on (100) GaAs by molecular beam epitaxy. As C source a graphite filament was used. Structures coherent with the substrate were obtained by adjusting properly the In and C concentrations. With simultaneous incorporation of In and C the strain is compensated and, consequently, the defect density is reduced. A maximum hole concentration value of p = 6×10 19 cm −3 was achieved, which is twice higher than the saturation value of C doping of GaAs produced under the same conditions. There is evidence that this value is not in the saturation limit. The product of the hole density times the mobility increases, so the resistance decreases with higher C doping. Raman spectra show that the C As peak broadens and shifts to lower frequencies for increasing concentration of indium. In H-passivated samples, Raman spectroscopy shows that C As is surrounded by Ga atoms only. Indium atoms are thus present only in the second group III shell. 相似文献
7.
The evolution of the gelation of silica gel was studied by means of Fourier transform infrared spectroscopy. The gel was prepared by hydrolysis and polycondensation of tetraethyl orthosilicate in the presence of water with HCl, and with formamide (DCCA) in methanol either added or not. For both systems the gelation process was followed by the time evolution of the ν-Si---O(H) and ν-Si---O(Si) absorption bands. In the systems which used formamide, the ν-Si---O(H) peak shifts from ≈ν = 950 cm −1 for τ = 0 to ≈ν = 968 cm −1 ( t = tgel) and tends to shifts to 975 cm −1 over a long period of time ( t = 100 tgel), and a slow rate evolution between 0.1 and 0.4 tgel is observed. In the absence of formamide the same evolution is observed without the slow rate plateau. For ν-Si-O(Si) absorption bands, the band near 1075 cm −1 remains practically unchanged in both systems during the experiment time, but the second absorption band at 1133 cm −1 is split into two bands each having its own specific evolution, depending on composition and temperature. 相似文献
8.
The (Pb 0.90La 0.10)TiO 3 [PLT] thick films (3.0 μm) with a PbO buffer layer were deposited on the Pt(1 1 1)/Ti/SiO 2/Si(1 0 0) substrates by RF magnetron sputtering method. The PLT thick films comprise five periodicities, the layer thicknesses of (Pb 0.90La 0.10)TiO 3 and PbO in one periodicity are fixed. The PbO buffer layer improves the phase purity and electrical properties of the PLT thick films. The microstructure and electrical properties of the PLT thick films with a PbO buffer layer were studied. The PLT thick films with a PbO buffer layer possess good electrical properties with the remnant polarization ( Pr=2.40 μC cm −2), coercive field ( Ec=18.2 kV cm −1), dielectric constant ( εr=139) and dielectric loss (tan δ=0.0206) at 1 kHz, and pyroelectric coefficient (9.20×10 −9 C cm −2 K −1). The result shows the PLT thick film with a PbO buffer layer is a good candidate for pyroelectric detector. 相似文献
9.
The infrared absorption spectra of sodium-disilicate glasses containing various amounts of Fe 2O 3 ([Na 2O · 2 SiO 2] 1−x [Fe 2O 3] x, where X = 0.05, 0.1 and 0.2) were investigated in the wavenumber range from 200–2000 cm −1. The addition of Fe 2O 3 to the sodium-disilicate glass does not seem to introduce any new absorption band as compared with the spectrum of a pure sodium-disilicate glass; nevertheless, a general shift of the existing absorption bands toward lower wavenumbers is observed. The amount of shift is, in fact, proportional to the content of Fe 2O 3 in the glass. This observation is consistent with the recently proposed structural model for the bonding of Fe 3+ ions in the iron-sodium-silicate glass system. Annealing of 20 mol% iron oxide glasses at 550 and 580°C produced an extra sharp infrared absorption peak at about 610 cm−1 wavenumber. This new peak is believed to be related to the crystallized particles of the glass as concluded from both a scanning electron micrograph and an electron diffraction pattern. 相似文献
10.
This paper reports the growth and spectral properties of 3.5 at% Nd 3+:LaVO 4 crystal with diameter of 20×15 mm 2 which has been grown by the Czochralski method. The spectral parameters were calculated based on Judd–Ofelt theory. The intensity parameters Ω λ are: Ω 2=2.102×10 −20 cm 2, Ω 4=3.871×10 −20 cm 2, Ω 6=3.235×10 −20 cm 2. The radiative lifetime τ r is 209 μs and calculated fluorescence branch ratios are: β 1(0.88μm)=45.2, β 2(1.06μm)=46.7, β 3(1.34μm)=8.1. The measured fluorescence lifetime τ f is 137 μm and the quantum efficiency η is 65.6%. The absorption band at 808 nm wavelength has an FWHM of 20 nm. The absorption and emission cross sections are 3×10 −20 and 6.13×10 −20 cm 2, respectively. 相似文献
11.
We report the results of a comprehensive study on the electrical, optical and crystalline properties of heavily carbon doped p-type (100) GaAs epilayers ( p = 6.3 × 10 18−1.3 × 10 20 cm -3; THICKNESS = 250−420 nm) grown by gas source molecular beam epitaxy using trimethylgallium and arsine. X-ray analysis showed epilayer lattice contraction with a mismatch of δ a/ a = -1.8 × 10 -3 at p = 1.3 × 10 20 cm -3. Room temperature photoluminescence peak energy shifted from 1.40 eV ( p = 6.3 × 10 18 cm -3) to 1.37 eV ( p = 1.3 × 10 20 cm -3). Stokes Raman spectra showed two modes assigned as the unscreened LO phonon (292 cm -1) and the low frequency branch of the coupled hole-plasmon-LO-phonon (266 cm -1). Conservation of Raman scattering rules under all incident light configurations showed that the (100) GaAs:C epilayers were of high crystalline quality without the presence of faceting or other such crystalline defects. Annealing at 900°C for between 30 s to 45 min, resulted in a significant reduction in the hole concentration, lattice contraction and photoluminescence intensity for all epilayers. The implications of these results for the development of GaAs/AlGaAs HBTs are discussed. 相似文献
12.
In a comparative study we have chosen TBAs and TBP as well as AsH 3 and PH 3 for the growth of InP/GaInAs(P) heterostructures for laser applications in a production metalorganic molecular beam epitaxy (MOMBE) system. The n-type doping was performed with Si from an effusion cell, whereas for the p-type doping Be and DEZn were utilized. InP layers using TBP under optimized cracking conditions exhibit excellent surface morphology with good electrical properties in the low 10 15 cm −3 range of carrier concentrations. The MOMBE growth mechanism is not disturbed by the hydride replacement compound. This allows for a convenient replacement without losing calibration data from the hydride process. Broad-area DH laserstructures with GaInAsP (λ = 1.55 μm) active regions were grown with AsH 3/PH 3 and TBAs/TBP. Comparable threshold current densities in the range of 1.6-2.3 kA/cm 2 are achieved for the lasers, grown with both sets of precursors combined with DEZn source doping. These results are in good agreement with the standard set by the hydride MOVPE process. 相似文献
13.
Heavily carbon-doped p-type In xGa 1−xAs (0≤ x<0.49) was successfully grown by gas-source molecular beam epitaxy using diiodomethane (CH 2I 2), triethylindium (TEIn), triethylgallium (TEGa) and AsH 3. Hole concentrations as high as 2.1×10 20 cm −3 were achieved in GaAs at an electrical activation efficiency of 100%. For In xGa 1−xAs, both the hole and the atomic carbon concentrations gradually decreased as the InAs mole fraction, x, increased from 0.41 to 0.49. Hole concentrations of 5.1×10 18 and 1.5×10 19 cm −3 for x = 0.49 and x = 0.41, respectively, were obtained by a preliminary experiment. After post-growth annealing (500°C, 5 min under As 4 pressure), the hole concentration increased to 6.2×10 18 cm −3 for x = 0.49, probably due to the activation of hydrogen-passivated carbon accepters. 相似文献
14.
Doped amorphous silicon films were prepared by plasma-enhanced chemical vapour deposition of silane and hydrogen mixtures, using phosphorus pentafluoride (PF 5) and boron trifluoride (BF 3) as dopant precursors. The films were studied by UV-vis spectroscopy and their photo and dark conductivity were measured, the latter as a function of temperature. The optical gap of the n-type samples, doped with PF 5, diminished as the concentration of this gas in the plasma was increased. However, the optical gap of p-type samples, doped with BF 3, did not show any appreciable optical gap decrease as the concentration of BF 3 was varied from 0.04% to 4.7%. The dark conductivity of the p-type films at these extremes of the doping range were 7.6 × 10 −10 and 3.5 × 10 −1 Ω −1 cm −1, respectively. 相似文献
15.
Drastic reduction of irregular defect density in molecular beam epitaxy (MBE) grown GaAs is obtained by using a novel arsenic Knudsen effusion cell with a cracking furnace. A surface defect density of less than 10 cm −2 is routinely achieved for continuously grown three 3-inch diameter, 1.7 μm thick, metal-semiconductor-field effect transistor (MESFET) structures when the cracking is carried out at about 700°C, which is the critical temperature for the conduction type change, and with the group III Knudsen cell only heated near the orifice of the crucible (top heat cell). These optimized cracking conditions also lead to successful mass production of some microwave devices with not only ultra-low defect density but suitable electrical performances. 相似文献
16.
Carbon doping of GaAs with carbon tetrabromide (CBr 4) in low pressure MOVPE has been investigated and applied to the fabrication of GaInP/GaAs HBTs. Especially the hydrogen incorporation and the associated acceptor passivation has been studied. The hydrogen found in single GaAs:C layers is predominantly incorporated during cooling the sample under AsH 3 after growth, n-Type capping layers can block this H indiffusion and GaAs:C base layers in HBTs show much lower H concentrations than GaAs:C single layers without a cap. A further reduction of acceptor passivation is possible by optimization of the growth procedure. First HBTs processed from layers with a base that was doped using CBr 4 show promising DC and HF performance (β = 45,
for 2 × 20 μm 2 devices). 相似文献
17.
A series of high quality δ-doped In 0.53Ga 0.47As samples have been grown lattice matched to InP with design doping densities in the range 2×10 12 to 5×10 12 cm −2. Analysis of the individual sub-band densities deduced from the Shubnikov-De Haas effect shows that both spreading and amphoteric behaviour increase with doping density. 相似文献
18.
Low-pressure metalorganic vapor phase epitaxy (LP-MOVPE) growth of carbon doped (InGa)P/GaAs and InP/(InGa)As heterojunction bipolar transistors (HBT) is presented using a non-gaseous source (ngs-) process. Liquid precursors TBAs/TBP for the group-V and DitBuSi/CBr 4 for the group-IV dopant sources are compared to the conventional hydrides AsH 3/PH 3 and dopant sources Si 2H 6/CCl 4 while using TMIn/TEGa in both cases. The thermal decomposition of the non gaseous sources fits much better to the need of low temperature growth for the application of carbon doped HBT. The doping behavior using DitBuSi/CBr 4 is studied by van der Pauw Hall measurements and will be compared to the results using Si 2H 6/CCl 4. Detailed high resolution X-ray diffraction (HRXRD) analysis based on 004 and 002 reflection measurements supported by simulations using BEDE RADS simulator enable a non-destructive layer stack characterization. InGaP/GaAs HBT structures designed for rf-applications are grown at a constant growth temperature of T gr=600°C and at a constant V/III-ratio of 10 for all GaAs layers. P-type carbon concentrations up to P = 5·10 19cm −3 and n-type doping concentrations up to N = 7·10 18cm −3 are achieved. The non self-aligned devices (A E = 3·10 μm 2)_show excellent performance, like a dc-current gain of B max = 80, a turn on voltage of V offset = 110 mV (Breakdown Voltage V CEBr,0 > 10 V), and radio frequency properties of f T/f max = 65 GHz/59 GHz. In the non-gaseous source configuration the strong reduction in the differences of V/III-ratios and temperatures during HBT structure growth enable easier LP-MOVPE process control. This is also found for the growth InP/InGaAs HBT where a high dc-current gain and high transit frequency of fT= 120 GHz are achieved. 相似文献
19.
Polycarbosilane (PC) is a precursor which is converted to Si xC 1−x fibers by pyrolysis in an inert gas atmosphere. The changes in the atomic vibrational spectrum during the conversion process from PC to Si xC 1−x have been examined by means of inelastic neutron scattering (INS) and infrared absorption (IR). The existence of transverse-optical(TO)- and longitudinal-optical(LO)-like phonon modes due to amorphous SiC clusters was established in the original and pyrolyzed PC by INS measurements. After pyrolyzing at 700–800°C, these modes appear distinctly around 730 and 930 cm −1, respectively, in the INS spectra. Pyrolysis at 1000°C makes these TO- and LO-like phonon modes sharper. 相似文献
20.
Solid solutions of Nd xLa 2−xcaB 10O 19 with different Na 3+ concentration have been synthesized by substituting Nd 3+ for La 3+ in La 2CaB 10O 19 Powder X-ray diffraction analysis shows that Nd 3+ is easy to incorporate into the crystal. Single crystal nd xLa 2−xCaB 10O 19 (NLCB) in centimeter size has been grown by Kyropoulos method. The crystal has strong absorption around 580nm and 805nm. The fluorescence spectra indicate that there is an energy transition at 1.06μm. And the SHG of NLCB is about the twice as that of KDP. These favorable features make NLCB a candidate for laser NLO multifunctional materials. 相似文献
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