Si(100)衬底上n-3C-SiC／p-Si异质结构研究

利用LPCVD方法在Si(100)衬底上获得了3C-SiC外延膜，扫描电子显微镜(SEM)研究表明3C-SiC／p—Si界面平整、光滑，无明显的坑洞形成。研究了以In和Al为接触电极的3C-SiC／p—Si异质结的I—V，C-V特性及I—V特性的温度依赖关系，比较了In电极的3C-SiC／p—Si异质结构和以SiGe作为缓冲层的3C-SiC／SiGe／p—Si异质结构的I—V特性，实验发现引入SiGe缓冲层后，器件的反向击穿电压由40V提高到70V以上。室温下A1电极3C-SiC／p—Si二极管的最大反向击穿电压接近100V，品质因子为1．95。

Heteroepitaxial Growth and Heterojunction Characteristics of Voids-Free n-3C-SiC on p-Si(100)

Highly oriented voids-free 3C-SiC heteroepitaxial layers are grown on φ50mm Si (100) substrates by low pressure chemical vapor deposition (LPCVD). The initial stage of carbonization and the surface morphology of carbonization layers of Si(100) are studied using reflection high energy electron diffraction (RHEED) and scanning electron microscopy (SEM). It is shown that the optimized carbonization temperature for the growth of voids-free 3S-SiC on Si (100) substrates is 1100 ℃. The electrical properties of SiC layers are characterized using Van der Pauw method. The I-V, C-V, and the temperature dependence of I-V characteristics in n-3C-SiC-p-Si heterojunctions with AuGeNi and Al electrical pads are investigated. It is shown that the maximum reverse breakdown voltage of the n-3C-SiC-p-Si heterojunction diodes reaches to 220V at room temperature. These results indicate that the SiC/Si heterojunction diode can be used to fabricate the wide bandgap emitter SiC/Si heterojunction bipolar transistors (HBT's).

Raman Investigatins of 3C-SiC Films Grown on Si (100) and Sapphire (0001) by LPCVD

The Raman measurements have been performed with the back-scattering geometry on the SiC films grown on Si(100) and sapphire (0001) by LPCVD. Typical TO and LO phonon peaks of 3C-SiC were observed for all the samples grown on Si and apphire substrates, indicating the epilayers are 3C-SiC polytype. Using a free-standing 3C-SiC film removed from Si(100) as a free-stress sample, the stresses of 3C-SiC on Si(100) and sapphire (0001) were estimated according to the shift of TO and LO phonons.

Improved Epitaxy of 3C-SiC Layers on Si(100) by New CVD/LPCVD System

Single crystalline 3C-SiC epitaxial layers are grown on φ50mm Si wafers by a new resistively heated CVD/LPCVD system, using SiH_4, C_2H_4 and H_2 as gas precursors. X-ray diffraction and Raman scattering measurements are used to investigate the crystallinity of the grown films. Electrical properties of the epitaxial 3C-SiC layers with thickness of 1 ～ 3μm are measured by Van der Pauw method. The improved Hall mobility reaches the highest value of 470cm~2/(V·s) at the carrier concentration of 7.7 * 10~(17)cm~(-3).

Si（001）衬底上APCVD生长3C-SiC薄膜的微孪晶及含量

于2010-11-23批量导入

Si（001）衬底上方形3C-SiC岛的LPCVD生长

于2010-11-23批量导入

In situ doping of 3C-SiC grown on (0001) sapphire substrates by LPCVD

The heteroepitaxial growth of n-type and p-type 3C-SiC on (0001) sapphire substrates has been performed with a supply of SiH4+C2H4+H-2 system by introducing ammonia (NH3) and diborane (B2H6) precursors, respectively, into gas mixtures. Intentionally incorporated nitrogen impurity levels were affected by changing the Si/C ratio within the growth reactor. As an acceptor, boron can be added uniformly into the growing 3C-SiC epilayers. Nitrogen-doped 3C-SiC epilayers were n-type conduction, and boron-doped epilayers were p-type and probably heavily compensated.

Raman study on residual strains in thin 3C-SiC epitaxial layers grown on Si(001)

Raman scattering measurement has been used to study the residual strains in the thin 3C-SiC/Si(001) epilayers with a variation of film thickness from 0.1 to 1.2 mu m. which were prepared by chemical vapor deposition (CVD)growth. Two methods have been exploited to figure our the residual strains and the exact LO bands. The final analyzing results show that residual strains exist in the 3C-SiC epilayers. The average stress is 1.3010 GPa, and the relative change of the lattice constant is 1.36 parts per thousand. Our measurements also show that 3C-SiC phonons are detectable even for the samples with film thickness in the range of 0.1 to 0.2 mu m. (C) 2000 Published by Elsevier Science S.A. All rights reserved.

Anisotropy of single crystal 3C-SiC during nanometric cutting

3C–SiC (the only polytype of SiC that resides in a diamond cubic lattice structure) is a relatively new material that exhibits most of the desirable engineering properties required for advanced electronic applications. The anisotropy exhibited by 3C–SiC during its nanometric cutting is significant, and the potential for its exploitation has yet to be fully investigated. This paper aims to understand the influence of crystal anisotropy of 3C–SiC on its cutting behaviour. A molecular dynamics simulation model was developed to simulate the nanometric cutting of single-crystal 3C–SiC in nine (9) distinct combinations of crystal orientations and cutting directions, i.e. (1?1?1) <-1?1?0>, (1?1?1) <-2?1?1>, (1?1?0) <-1?1?0>, (1?1?0) <0?0?1>, (1?1?0) <1?1?-2>, (0?0?1) <-1?1?0>, (0?0?1) <1?0?0>, (1?1?-2) <1?-1?0> and (1?-2?0) <2?1?0>.

In order to ensure the reliability of the simulation results, two separate simulation trials were carried out with different machining parameters. In the first trial, a cutting tool rake angle of -25°, d/r (uncut chip thickness/cutting edge radius) ratio of 0.57 and cutting velocity of 10 m s-1 were used whereas a second trial was done using a cutting tool rake angle of -30°, d/r ratio of 1 and cutting velocity of 4 m s-1. Both the trials showed similar anisotropic variation.

The simulated orthogonal components of thrust force in 3C–SiC showed a variation of up to 45%, while the resultant cutting forces showed a variation of 37%. This suggests that 3C–SiC is highly anisotropic in its ease of deformation. These results corroborate with the experimentally observed anisotropic variation of 43.6% in Young's modulus of 3C–SiC. The recently developed dislocation extraction algorithm (DXA) [1, 2] was employed to detect the nucleation of dislocations in the MD simulations of varying cutting orientations and cutting directions. Based on the overall analysis, it was found that 3C–SiC offers ease of deformation on either (1?1?1) <-1?1?0>, (1?1?0) <0?0?1>, or (1?0?0) <1?0?0> setups.

Obtención de nanopartículas de 3C-SiC por medio de una síntesis Sol-Gel asistida por microondas.

Tesis (Maestría en Ciencias de la Ingeniería Mecánica con Especialidad en Materiales) UANL, 2010.

Solar driven energy conversion applications based on 3C-SiC

There is a strong and growing worldwide research on exploring renewable energy resources. Solar energy is the most abundant, inexhaustible and clean energy source, but there are profound material challenges to capture, convert and store solar energy. In this work, we explore 3C-SiC as an attractive material towards solar-driven energy conversion applications: (i) Boron doped 3C-SiC as candidate for an intermediate band photovoltaic material, and (ii) 3C-SiC as a photoelectrode for solar-driven water splitting. Absorption spectrum of boron doped 3C-SiC shows a deep energy level at ~0.7 eV above the valence band edge. This indicates that boron doped 3C-SiC may be a good candidate as an intermediate band photovoltaic material, and that bulk like 3C-SiC can have sufficient quality to be a promising electrode for photoelectrochemical water splitting.

Controlling the surface roughness of epitaxial SiC on silicon

The surface of cubic silicon carbide (3C-SiC) hetero-epitaxial films grown on the (111) surface of silicon is a promising template for the subsequent epitaxial growth of III-V semiconductor layers and graphene. We investigate growth and post-growth approaches for controlling the surface roughness of epitaxial SiC to produce an optimal template. We first explore 3C-SiC growth on various degrees of offcut Si(111) substrates, although we observe that the SiC roughness tends to worsen as the degree of offcut increases. Hence we focus on post-growth approaches available on full wafers, comparing chemical mechanical polishing (CMP) and a novel plasma smoothening process. The CMP leads to a dramatic improvement, bringing the SiC surface roughness down to sub-nanometer level, though removing about 200 nm of the SiC layer. On the other hand, our proposed HCl plasma process appears very effective in smoothening selectively the sharpest surface topography, leading up to 30% improvement in SiC roughness with only about 50 nm thickness loss. We propose a simple physical model explaining the action of the plasma smoothening.

Time evolution of graphene growth on SiC as a function of annealing temperature

We followed by X-ray Photoelectron Spectroscopy (XPS) the time evolution of graphene layers obtained by annealing 3C SiC(111)/Si(111) crystals at different temperatures. The intensity of the carbon signal provides a quantification of the graphene thickness as a function of the annealing time, which follows a power law with exponent 0.5. We show that a kinetic model, based on a bottom-up growth mechanism, provides a full explanation to the evolution of the graphene thickness as a function of time, allowing to calculate the effective activation energy of the process and the energy barriers, in excellent agreement with previous theoretical results. Our study provides a complete and exhaustive picture of Si diffusion into the SiC matrix, establishing the conditions for a perfect control of the graphene growth by Si sublimation.

Micro-raman investigation of defects in a 4H-SiC homoepilayer

Three types of defects, namely defect I, defect 11, defect 111, in the 4H-SiC homoepilayer were investigated by micro-raman scattering measurement. These defects all originate from a certain core and are composed of (1) a wavy tail region, (11) two long tails, the so called comet and (111) three plaits. It was found that there are 3C-SiC inclusions in the cores of defect 11 and defect III and the shape of inclusion determines the type of defect II or defect III. If the core contains a triangle-shaped inclusion, the defect III would be formed; otherwise, the defect 11 was formed. No inclusion was observed in the core of the defect I. The mechanisms of these defects are discussed.