Materials Science Forum Vol. 1014

Abstract: The growth pits formed during 5-10 μm 4H-SiC epitaxial growth by a home-built vertical hot-wall CVD reactor are investigated and their formation mechanisms are discussed. The origin of the growth pits is believed to be the silicon droplets related to the unoptimized growth condition. The growth pits are successfully removed by adding more HCl to the in-situ etching stage and the after-growth cooling stage.

Abstract: Diamond is arguably the best candidate material for heat dissipation applications, especially in high-power electronic devices. Silicon carbide (SiC) is a kind of wide band gap material, which can be used in applications of silicon (Si) components to reach the performance limits. In this paper, thin diamond films were successfully deposited on C-face and Si-face of 6H-SiC substrates respectively using MPCVD at temperatures from 800 to 1050 °C. SEM images indicated the growth quality comparison of the two faces of SiC. The diffraction peaks of the diamond (111), (220), and (311) crystal planes can be observed by XRD measurement, and the intensity of the diamond diffraction peaks grown on the C-face is stronger than that on Si-face. The growth process was analyzed by Raman spectrum. FWHM of diamond Raman spectra on Si-face and C-face are 6.07cm^-1 and 5.47cm^-1 respectively. All above measurement results show that the diamond grown on the C-face has higher crystal quality than that on Si-face of SiC.

Abstract: In this study, the effect of a high-temperature annealing process on AlN is investigated. The high-temperature annealing process reduces the screw dislocation density of the AlN film to 2.1x10⁷ cm^-2. The AlN surface is highly flat. Through HRXRD and Raman spectroscopy, the stress mode changes in the sputtered AlN film before and after high-temperature annealing were studied in depth. Based on the HTA-AlN template, a high-quality, high-Al composition AlGaN epitaxial wafer, with a (0002) plane rocking curve FWHM of 246 arcsec , was prepared at 1080°C The growth mode of AlGaN grown directly on the AlN template at low temperature is summarized.

Abstract: In this work, In₂O₃ thin films were grown on (111) yttria-stabilized zirconia (YSZ) by metal-organic chemical vapor deposition (MOCVD) at different temperature. It is found that samples grown at low temperature showed lower residual stress but higher mosaicity while high growth temperatures could also cause deterioration in crystal quality due to increasing lattice mismatch. To obtain high quality In₂O₃ film with low residual strain, a 30-nm thick layer grown at 530 °C was introduced as buffer layer, considering both stress relaxation and crystalline mosaicity. By using two-step growth method, a 400 nm-thick, high quality, near-strain-free In₂O₃ thin film with the full width at half maximum (FWHM) values of (222) diffraction peaks being as narrow as 648 arcsec was successfully obtained.

Abstract: In this paper, polycrystal Ga2O3 thin films were grown on crystal n+-Si substrates by solution process. The XRD profile revealed that monoclinic β-Ga2O3 and rhombohedral α-Ga2O3 were coexisting in the film. The solution-process Ga2O3 film exhibited an ultrahigh transmittance (>97%) to a wavelength range of 280 nm~800 nm. The optical bandgap of ~5.0 eV and breakdown field of 4.2 MV/cm of the Ga2O3 thin film was obtained. Dielectric parameters such as capacitance, dielectric permittivity and loss tangent were investigated. It was observed that these parameters have a strong dependence on frequency.

Abstract: The triangular defect is a common defect in the 4H-SiC epitaxy, which is also one of the killer defects to the 4H-SiC devices. In this paper, the 4H-SiC epitaxial wafer was grown by chemical vapor deposition (CVD). The formation mechanism of triangular defects in silicon carbide epitaxy was analyzed, and the solutions were proposed. Then, the diodes were fabricated on the wafer, and the influence of triangular defects on the forward and reverse I-V characteristics of 4H-SiC diodes was analyzed by tracking the defects map. The results show that the presence of triangular defects can lead to the reduction of the reverse voltage by about 40%, an increase of the leakage current by four orders of magnitude, and an increase of the forward conduction resistance.

Abstract: By using a NAURA Advanced Physical Vapor Transport (PVT) System, the character ofthe synthesized SiC powder were studied. Mainly from the aspects of purity and particle size, and relevant experiments were designed to understand the influence of the powder source on the synthesized SiC powder. The results showed that the selection of Si powder source with appropriate particle size was conducive to increase the proportion of large particle size of SiC powder. In addition, the purification of material source in the early stage of the process was beneficial to improve the purity of SiC powder. The results showed successful preparation of optimized SiC powder and thus high-quality SiC wafers were made.

Abstract: Epitaxial GaAs-on-Si is an ideal material system for studying the physics of mismatched heteroepitaxy of a polar semiconductor layer grown on a non-polar substrate like silicon. Understanding and optimization of the initial nucleation of GaAs on silicon is the most crucial step in the success of GaAs/Si heteroepitaxy. Molecular beam epitaxy (MBE) technique has been used to deposit hetero-epitaxial GaAs thin-film on off-angle Si (100) substrate using the three-step growth method. After optimizing the growth parameters of low temperature (LT) buffer layer and high temperature (HT) epilayer, XRD analyses were performed. Characterization results of the GaAs (004) films which were not subjected to annealing, show a full-width half maximum (FWHM) of 760.1 arc sec and a root mean square (RMS) surface roughness of lower than 1 nm for a scanning area of 10 μm × 10 μm.

Abstract: In this paper, a new model is established ,which aimed at the physical model and analytical model structure,and ombined with the nonlinear capacitance and parasitic parameters of SiC. The accuracy and rapidity of the model are preserved as much as possible. This paper firstly compares and analyzes the established models through theoretical analysis of new models and SIMetrix/SIMPLIS platforms. Then the paper analyzes the switching characteristics of the SiC and verify the accuracy of the verification results by setting up a double pulse platform experiment. Finally, by analyzing the physical, high temperature, static and dynamic characteristics of SiC and Si, the reference values of driving voltage design of SiC and the comparative data of SiC and Si losses are obtained by means of the double pulse experimental platform, which is used to analyze the physical characteristics, high temperature resistance, static characteristics and dynamic characteristics of SiC. Thus better play the superior performance of SiC.