DLTS study of 3C-SiC grown on Si using hexamethyldisilane
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DLTS study of 3C-SiC grown on Si using hexamethyldisilane M. Kato, M. Ichimura, E. Arai, Y. Masuda*, Y. Chen*, S. Nishino*, Y. Tokuda** Department of Electrical and Computer Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 Japan *Department of Electronics and Information Science, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 Japan **Department of Electronics, Aichi Institute of Technology, Yakusa, Toyota 470-0392 Japan
ABSTRACT n-type 3C-SiC was heteroepitaxially grown on n-type Si(100) substrates using HMDS (hexamethyldisilane) and characterized by DLTS (deep level transient spectroscopy) measurements. In order to investigate relationship of defect density with epilayer thickness, epilayers with various thicknesses were grown. Relatively thin (2.2µm thick) epilayers contain a defect with an activation energy of 0.25eV. This defect level is slightly shallower than that in 3C-SiC grown by SiH4 and C3H8 (~0.3eV).
INTRODUCTION SiC is a promising material for high-temperature, high-power and high-frequency electronic devices because of its large band-gap, high thermal conductivity and high electron saturation velocity. In contrast to other polytypes, 3C-SiC can be grown heteroepitaxially on Si substrates, and this can lead to mass-production of SiC wafers. Therefore, low-cost SiC devices can be fabricated from 3C-SiC. However the 3C-SiC/Si interface may introduce extended defects in epitaxial films due to large difference in thermal expansion coefficient and lattice constant. Point defects can also be formed because of intrinsic nature of the material or the growth reaction. Defects in epilayers frequently have deep levels in the energy gap which degrade the operation of semiconductor devices. Therefore it is important to investigate deep-level defects in 3C-SiC/Si epilayers. Usually 3C-SiC is grown by the CVD (chemical vapor deposition) method using SiH4+C3H8 with H2 carrier gas. In this work, we employed DLTS (deep level transient spectroscopy) method to characterize deep level defects in 3C-SiC grown by CVD using HMDS (hexamethyldisilane:Si2(CH3)6). This gas system has the advantages of safety and large deposition rate over the conventional gas system [1]. Type and/or density of defects formed in the epilayer bulk may depend on gas species used in the growth. To the best of our knowledge, although the reports of DLTS study for 3C-SiC/Si grown by the conventional gas system were published [2-5], no report has been published about DLTS of 3C-SiC/Si grown from HMDS. To investigate defects originating from the heterointerface, the 3C-SiC films with several thicknesses were grown. We detected two kinds of defects; one is attributed to the heteroepitaxy and the other formed in the epilayer bulk.
T4.3.1
Table I. Thickness and net donor concentration of 3C-SiC ("-" represents that the Schottky diode shows poor rectifying characteristic.) Net donor concentration (cm-3) Thickness (µm) 0.65 1.2×1018 1.0 1.1×1018 2.2 3.8×1017 2.6 6.5×1017 3.2 3.8×1017 4.3 6.6 4.4×1017
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