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1.
Hopping conduction and its photoquenching in molecular beam epitaxial GaAs grown at low temperatures
As the growth temperature of molecular beam epitaxial GaAs is increased from 250 to 400°C, the dominant conduction changes
from hopping conduction to band conduction with a donor activation energy of 0.65 eV. A 300°C grown layer is especially interesting
because each conduction mechanism is dominant in a particular temperature range, hopping below 300K and band conduction above.
Below 140K, the hopping conduction is greatly diminished (quenched) by irradiation with either infrared (hv≤1.12 eV) or 1.46
eV light, but then recovers above 140K with exactly the same thermal kinetics as are found for the famous EL2. Thus, the 0.65
eV donor, which is responsible for both the hopping and band conduction, is very similar to EL2, but not identical because
of the different activation energy (0.65 eV vs 0.75 eV for EL2). 相似文献
2.
Yuheng Zeng Deren Yang Xiangyang Ma Zhidan Zeng Duanlin Que Longfei Gong Daxi Tian Liben Li 《Materials Science in Semiconductor Processing》2008,11(4):131-136
Delineation of defects in the heavily doped n-type Czochralski silicon wafers by preferential etching is an issue not having been essentially solved. Herein, a chromium-free etchant based on HNO3–HF–H2O system, with an optimum volume ratio of VHNO3%:VHF%:VH2O%=20%:45%:35%, has been developed. It can reveal well the defects such as dislocation and oxygen precipitation-induced bulk microdefects (BMDs) in the heavily doped n-type silicon wafers with resistivities even lower than 1 mΩ cm. Moreover, this etchant is appropriate to delineate the defects on (1 1 1), (1 1 0) or (1 0 0) surface of silicon crystal. Furthermore, the density of oxygen precipitation-induced BMDs in the heavily doped n-type silicon wafers derived from the preferential etching using this newly developed etchant correlates well with that derived from scanning infrared microscopy (SIRM) within its detection limit. 相似文献
3.
《Solid-state electronics》2011,57(1):1-8
Hydrogenated amorphous silicon carbide (a-SiCx:H) films of different carbon content (x) were deposited by radio frequency plasma enhanced chemical vapor deposition (PECVD) system. Apart from the X-ray photoelectron spectroscopy (XPS) and UV-Visible transmission analyses, the resistivity measurements between 293 K and 450 K were emphasized to assess the eventual transport mechanisms. The film resistivities are unexpectedly found relatively low, especially for high carbon content. In the frame of exclusive band conduction, the apparent thermal activation energies, evaluated from Arrhenius type plot remain too low compared to half values of the optical gaps.Numerical analyses were undertaken by extending conduction from the band conduction about the mobility edge inside the band gap by including the nearest neighbor hopping (NNH) conduction across the localized tail states. By successfully fitting the formulated conductivity expression to the experimental results, parameters such as tail states distributions, true activation energies to the mobility edge have been retrieved. 相似文献
4.
W. C. Mitchel Matthew Roth A. O. Evwaraye P. W. Yu S. R. Smith 《Journal of Electronic Materials》1996,25(5):863-867
The electronic properties of boron in bulk 6H-SiC have been studied by temperature dependent Hall effect, thermal admittance
spectroscopy, and optical absorption. A single acceptor level located between 0.27 and 0.35 eV above the valence band is associated
with boron on a silicon lattice site. The deep nature of this acceptor level prevents complete thermal activation of the level
at room temperature and thus carrier concentration measurements at this temperature will not give the total boron concentration.
A spread in the measured activation energy for boron is reported. Measurement of optical absorption is suggested as a nondestructive
measure of boron concentration. No evidence for the D-center was observed in this material. 相似文献
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6.
N-type layers in GaAs with high free electron concentrations have been produced by multiple implantation of Ga, As, or P with
dopant species such as Se, Si, or Ge. The implants that have been investigated include Si, Si + P, Ge, Ge + As, Se, and Se
+ Ga. The multiple implants Si + P, Ge + As, and Se + Ga gave higher peak carrier concentrations, especially at lower anneal
temperatures, than did the respective single implants Si, Ge, and Se. In fact, Ge when implanted alone produced a p-type layer
while the Ge + As multiple implant produced an n-type layer. Multiple implants with Si and Ge as dopants showed significant
thermal diffusion during the anneal. Multiple implants of Ga with Se, on the other hand, resulted in reduced thermal diffusion
in comparison with single Se implants. 相似文献
7.
Inductively coupled plasma (ICP) etching of single crystal 6H-silicon carbide (SIC) is investigated using oxygen (O2)-added sulfur hexafluoride (SF6) plasmas. The relations between the microtrenching effect and ICP coil power, the composition of the etch gases and different bias voltages are discussed. Experimental results show that the microtrench is caused by the formation of a SiFxOy layer, which has a greater tendency to charge than SiC, after the addition of O2. The microtrenching effect tends to increase as the ICP coil power and bias voltage increase. In addition, the angular distribution of the incident ions and radicals also affects the shape of the microtrench. 相似文献
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10.
SiG高温氧化的研究 总被引:1,自引:1,他引:0
热氧化是碳化硅晶片工艺中一种常用的工艺,但基于硅工艺的氧化温度一般都相对较低,此温度下,碳化硅氧化缓慢,在很多情况下很难满足工艺需求.利用新设计的高温氧化设备对碳化硅晶片进行不同温度下的氧化实验.实验结果显示,高温下,碳化硅氧化速度加快,温度的增加对氧化速度影响极大,以1 200℃时的氧化速率为基准,1 250℃时的氧化速率是1 200℃时的1.5倍;1 300℃下的氧化速率能达到1 200℃的2倍;而在1 350 ℃时,氧化速度已经将近1 200 ℃时的3倍. 相似文献
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12.
T. Marshall J. A. Petruzzello S. P. Herko J. M. Gaines C. A. Ponzoni 《Journal of Electronic Materials》1994,23(3):255-258
Significant progress in improving the performance of blue-green II-VI semiconductor injection lasers has come about from advances
in the epitaxial growth and doping of ZnMgSSe on GaAs substrates. This paper investigates electrical transport and its relation
to structural quality in n-type Zn1-yMgy SxSe1-x epilayers doped with Cl, grown by molecular beam epitaxy. The composition parameters x and y vary from about 0.12-0.18 and
0.08-0.15, respectively. The quaternary epilayers studied are lattice-matched (or nearly so) to the GaAs substrate. Temperature-dependent
Hall-effect measurements are performed on seven n-type ZnMgSSe:Cl epilayers, and a technique is presented whereby the resulting
mobility-vs-temperature data is compared with data for ZnSe to obtain a structural figure of merit that is useful in characterizing
the quaternary epilayer. 相似文献
13.
J. M. Andrews 《Journal of Electronic Materials》1979,8(3):227-247
Undoped polycrystalline silicon (poly-Si) films, 0.5 μm thick, have been prepared at 700‡C by chemical vapor deposition (CVD)
onto thermally oxidized n+-Si substrates. The impurity concentration was varied by implanting with As, P, and Sb ions, accelerated to 30 keV; total
doses ranged from 2×1011 to 3×1015 ions/cm2. Sheet resistance measurements, spanning 8 orders of magnitude, were made as a function of implantation dose. A reduction
of 6 orders of magntiude in poly-Si sheet resistance took place within the implantation dose range between 1012 and 1014 ions/cm2. Some samples also exhibited large reductions in sheet resistance following the standard heat treatment for Al contact sintering
and surface state reduction, which is normally at 450‡C for 0.5 hr in H2. Sheet resistance measurements were also made as a function of temperature in the range 0 to 315‡C. The effective activation
energy for electrical conduction depends upon implantation dose. At low doses (2×1011cm−2) the poly-Si is intrinsic, withE
A
= 0.65 eV. At a dose of 1015 cm−2, electrical conduction is a weak function of temperature, withE
A
= 0.027 eV. 相似文献
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15.
Manuel Schnabel Mariaconcetta Canino Kai Schillinger Philipp Lper Caterina Summonte Peter R. Wilshaw Stefan Janz 《Progress in Photovoltaics: Research and Applications》2016,24(9):1165-1177
Monolithic tandem cells involving a top cell with Si nanocrystals embedded in SiC (Si NC/SiC) and a c‐Si bottom cell have been prepared. Scanning electron microscopy shows that the intended cell architecture is achieved and that it survives the 1100 °C anneal required to form Si NCs. The cells exhibit mean open‐circuit voltages Voc of 900–950 mV, demonstrating tandem cell functionality, with ≤580 mV arising from the c‐Si bottom cell and ≥320 mV arising from the Si NC/SiC top cell. The cells are successfully connected using a SiC/Si tunnelling recombination junction that results in very little voltage loss. The short‐circuit current densities jsc are, at 0.8–0.9 mAcm−2, rather low and found to be limited by current collection in the top cell. However, equivalent circuit simulations demonstrate that in current‐mismatched tandem cells such as the ones studied here, higher jsc, when accompanied by decreased Voc, can arise from shunts or breakdown in the limiting cell rather than improved current collection from the limiting cell. This indicates that Voc is a better optimisation parameter than jsc for tandem cells where the limiting cell exhibits poor junction characteristics. The high‐temperature‐stable cell architecture developed in this work, coupled with simulations highlighting potential pitfalls in tandem cell analysis, provides a suitable route for optimisation of Si NC layers for photovoltaics on a tandem cell device level. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
16.
The Seebeck coefficient is determined from silicon microchannel plates (Si MCPs) prepared by photo-assisted electrochemical etching at room temperature (25 ℃). The coefficient of the sample with a pore size of 5 × 5 μm2, spacing of 1 μm and thickness of about 150 μm is -852 μV/K along the edge of the square pore. After doping with boron and phosphorus, the Seebeck coefficient diminishes to 256 μV/K and -117 μV/K along the edge of the square pore, whereas the electrical resistivity values are 7.5 × 10-3 Ω·cm and 1.9 × 10-3 Ω·cm, respectively. Our data imply that the Seebeck coefficient of the Si MCPs is related to the electrical resistivity and is consistent with that of bulk silicon. Based on the boron and phosphorus doped samples, a simple device is fabricated to connect the two type Si MCPs to evaluate the Peltier effect. When a proper current passes through the device, the Peltier effect is evidently observed. Based on the experimental data and the theoretical calculation, the estimated intrinsic figure of merit ZT of the unicouple device and thermal conductivity of the Si MCPs are 0.007 and 50 W/(m·K), respectively. 相似文献
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18.
采用自主开发的SiC外延材料和工艺技术,相继实现了S波段连续波状态下输出功率瓦级和10 W的SiC MESFET。经过版图设计的改进和工艺条件的优化,取得了S波段连续波状态下输出功率大于20 W,功率增益大于12 dB,功率附加效率大于30%的SiC MESFET研制结果。器件的功率增益和输出功率较以往的研制结果均得到显著提高,器件的反向截止泄漏电流也大幅度降低。由于器件未采用内匹配结构,其体积也比一般内匹配器件的体积小。研制结果为多胞合成实现更大功率输出的器件创造了条件,也使S波段连续波大功率输出器件的研制水平上了一个新的台阶。 相似文献
19.
The Seebeck coefficient is determined from silicon microchannel plates(Si MCPs) prepared by photoassisted electrochemical etching at room temperature(25℃).The coefficient of the sample with a pore size of 5×5μm2,spacing of 1μm and thickness of about 150μm is -852μV/K.along the edge of the square pore.After doping with boron and phosphorus,the Seebeck coefficient diminishes to 256μV/K and -117μV/K along the edge of the square pore,whereas the electrical resistivity values are 7.5×10-3Ω·cm and 1.9×10-3Ω·cm,respectively. Our data imply that the Seebeck coefficient of the Si MCPs is related to the electrical resistivity and is consistent with that of bulk silicon.Based on the boron and phosphorus doped samples,a simple device is fabricated to connect the two type Si MCPs to evaluate the Peltier effect.When a proper current passes through the device,the Peltier effect is evidently observed.Based on the experimental data and the theoretical calculation,the estimated intrinsic figure of merit ZT of the unicouple device and thermal conductivity of the Si MCPs are 0.007 and 50 W/(m·K), respectively. 相似文献
20.
Here we discuss the synthesis of copper(II)oxide(CuO)and manganese(Mn)-doped CuO thin films varying with 0 to 8 at%Mn using the spray pyrolysis technique.As-deposited film surfaces comprised of agglomerated spherical nanoparticles and a semi-spongy porous structure for 4 at%Mn doping.Energy dispersive analysis of X-rays confirmed the chemical composi-tion of the films.X-ray diffraction spectra showed a polycrystalline monoclinic structure with the predominance of the(11)peak.Optical band gap energy for direct and indirect transitions was estimated in the ranges from 2.67-2.90 eV and 0.11-1.73 eV,respectively.Refractive index and static dielectric constants were computed from the optical spectra.Electrical resistivity of CuO and Mn-doped CuO(Mn:CuO)thin films was found in the range from 10.5 to 28.6Ω·cm.The tiniest electron effective mass was calculated for 4 at%Mn:CuO thin films.P to n-type transition was observed for 4 at%Mn doping in CuO films.Carrier con-centration and mobility were found in the orders of 1017cm-3and 10-1cm2/(V·s),respectively.The Hall coefficient was found to be between 9.9 and 29.8 cm3/C.The above results suggest the suitability of Mn:CuO thin films in optoelectronic applications. 相似文献