SiC epitaxial growth on porous SiC substrates
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SiC epitaxial growth on porous SiC substrates G. Melnychuck,1 M. Mynbaeva,2 S. Rendakova,3 V. Dmitriev,2,3 and S. E. Saddow1 1
Emerging Materials Research Laboratory, Department of Electrical & Computer Engineering, Mississippi State, MS 39762-9571 2 Ioffe Institute, St. Petersburg, 194021 Russia 3 TDI, Inc., Gaithersburg, MD, 20877
Abstract We report on the growth and crystal quality of CVD epitaxial layers grown on porous SiC (PSC) substrates. A layer of porous SiC was fabricated by surface anodization of commercial 4H and 6H-SiC (0001)Si face off-axis wafers. The 4H and 6H-SiC epilayers were grown on porous SiC (PSC) substrates using atmospheric pressure CVD at 1580°C and a Si to C ratio of 0.3. Results of X-ray diffraction, RHEED, SEM and AFM characterization demonstrated good surface quality of the films grown on porous material. PL data indicate a greatly improved defect structure in the epi layers grown on PSC as compared to control samples. Preliminary etch pit experiments to estimate the dislocation density indicate a three-fold reduction in defect density in the epi material grown on PSC substrates as compared to epi grown conventional substrates. Introduction The presence of micropipes and dislocations in SiC wafers used as substrates for SiC epitaxial growth may cause formation of lattice defects in the epilayers. The objective of this research was to develop a chemical vapor deposition (CVD) growth technique on porous SiC [1] substrates in order to reduce the concentration of structural defects in SiC epilayers. Porous SiC (PSC) has been developed for numerous applications, such as power device passivation [2], and as buffer layers for GaN epitaxial growth [3]. A PSC layer is formed on a conventional SiC substrate (either 4H or 6H-SiC) via the anodisation of the substrate in aqueous HF [3]. The PSC layer was observed to extend approximately 5 µm into the SiC substrate thus forming a PSC layer for subsequent epitaxial layer growth. Using a horizontal cold-wall chemical vapor deposition (CVD) system, 5 µm thick SiC epitaxial layers were grown simultaneously on both PSC and standard (i.e., ‘control’) substrates using a standard dual-precursor CVD growth technique in the Emerging Materials Research Laboratory [4]. The substrates were 3.5 and 8 ° off-axis from the (0001) Si face for 6H and 4H-SiC, respectively. The ratio of silicon to carbon was 0.3 and the growth temperature 1580 °C. The net doping density in CVD layers was measured to be approximately 1.5 × 1015 cm−3 as measured with deposited Schottky barrier diodes using the CV technique.
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Mat. Res. Soc. Symp. Vol. 622 © 2000 Materials Research Society
Material Characterization After CVD growth, the samples were cleaved and the epitaxial layer quality observed under an SEM. Figure 1 shows the results from a 4H PSC epitaxial layer grown using the growth conditions discussed above. Note that the pores abruptly end at the interface with a high-quality epitaxial layer having been formed on top. Surface characterization was performed on this sampl
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