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<strong>BUITEMS</strong> Quality & Excellence in Education Characterization of SiC by means of C-V measurement of respective schottky diode by DLTS (Sweden). An epilayer of ~35 μm thick was grown on the SiC substrate by chemical vapor deposition (CVD) growth. Nitrogen dopant atoms were incorporated during the epitaxial growth sequence (Lin and Chang, 1995; Suzuki and Koizumi, 2004). Circular Schottky contact of 0.8mm diameter using Au and Ni separately was made by thermal evaporation. Capacitance-Voltage C-V Measurements The C-V measurements are necessary to determine the diode quality as well as to determine depth profile. At different temperatures capacitance voltage measurements were taken for various materials. From the C-V measurement we find the carrier concentration, built-inpotential and depth profile: Doping concentration ‘N d ’, Built-in potential ‘V bi ’ and Depth profile ‘depth vs. N d , N d = 2/[qε m* slope] (1) V bi = [intercept*qε m N d]/2 (2) Nd = [2(V a + V bi)]/ [qε md/dv(A 2 /C 2 )] (3) And D(C) = ε mA/C Where V a = Applied voltage, V bi = Built-in potential, q = Electron charge, Temperatur e (T) K Built in Doping (N d ) cm -3 (V bi ) V Concentration potential 295K 5.2061·10 12 1.49 320K 1.1402·10 13 0.90 340K 2.8920·10 13 0.72 360K 7.8894·10 13 0.52 380K 1.3945·10 14 0.60 400K 2.5968·10 14 0.54 Table: 1 Parameters calculated from CV measurements of 6H-SiC From table 1 we observed that the doping concentration and built-in potential was effected by temperature. The value of Nd at room temperature was determined 5.2061 ·10 12 cm -3 which increased with the increase in temperature. While the value of Vbi at room temperature calculated as 1.49V and gradually lowered on increasing temperature and measured 0.54V at 400K also an unsequence value of Vbi determined at 360K. ε m = Relative permittivity of the material, D = Depth RESULTS AND DISCUSSION Capacitance-Voltage C-V Measurements of SiC The typical C-V characteristics of n-type 6H-SiC as grown at different temperatures 295K to 400K are shown in Figures 1 to 12. In the graphs of Voltage (V) and (A/C the straight line is taken as the theoretical linear fitting of the curves. The graphs of depth profiles have taken between depth and doping concentration shown in Figures 13 and 14. Using equations (1) and (2) and for depth profile using equation (3) we calculated the following parameters shown in table below. Fig 1. The graph between C-V of SiC at T=295K. 26
<strong>BUITEMS</strong> Quality & Excellence in Education Characterization of SiC by means of C-V measurement of respective schottky diode by DLTS 7.00E+018 6.0 6.00E+018 5.5 (A/C) 2 cm 4 F -2 5.00E+018 4.00E+018 3.00E+018 Capacitance (pF) 5.0 4.5 4.0 2.00E+018 3.5 1.00E+018 -5 -4 -3 -2 -1 0 Voltage (V) Fig 2. The graph between V and (A/C ) 2 of SiC at T=295K. -5 -4 -3 -2 -1 0 Voltage (V) Fig 5. The graph between C-V of SiC at T=340K. 2.00E+018 4.5 1.80E+018 1.60E+018 Capacitance (pF) 4.0 3.5 3.0 (A/C) 2 cm 4 F -2 1.40E+018 1.20E+018 1.00E+018 8.00E+017 2.5 6.00E+017 -5 -4 -3 -2 -1 0 Voltage (V) -5 -4 -3 -2 -1 0 Voltage (V) Fig 6. The graph between V and (A/C ) 2 of SiC at T=340K Fig 3. The graph between C-V of SiC at T=320K (A/C) 2 cm 4 F -2 4.50E+018 4.00E+018 3.50E+018 3.00E+018 2.50E+018 2.00E+018 Capacitance (pF) 9.5 9.0 8.5 8.0 7.5 7.0 6.5 1.50E+018 1.00E+018 -6 -5 -4 -3 -2 -1 0 1 2 Voltage (V) 6.0 5.5 -5 -4 -3 -2 -1 0 Voltage (V) Fig 4. The graph between V and (A/C ) 2 of SiC at T=320K Fig 7. The graph between C-V of SiC at T=360K. 27
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