1. ELECT 871 12/01/03 SiC basic properties The basic properties of SiC makes it a material of choice for fabricating devices operating at high power and high temperature Property Band gap (eV) Breakdown field for 10 17 cm -3 (MV/cm) Saturated Electron Drift (cm/s) Electron mobility (cm 2 /Vs) Hole mobility (cm 2 /Vs) Thermal Conductivity (W/cmK) Si 1.1 0.6 10 7 1350 450 1.5 GaAs 1.42 0.65 1x10 7 6000 330 0.46 4H-SiC 3.2 3-5 2x10 7 <900 <120 4.9 3C-SiC 2.36 1.5 2.5x10 7 <800 <320 5.0 GaN 3.4 3.5 1.5x10 7 1000 300 1.3 6H-SiC 3.0 3-5 2.5x10 7 <400 <90 4.9

2. ELECT 871 12/01/03 SiC growth processes Figure modified after Matsunami et al., Amorphous and Crystalline Silicon Carbide, Springer- Verlag, Proceedings in Physics, V. 34 (1989) pp. 34-39. DPB defects result from change in stacking of atomic layers in hetero-epitaxial growth

3. ELECT 871 12/01/03 SiC growth features AFM image around a dislocation core in 4H- SiC 0.5 nm (two Si-C bilayers) and 1.0 nm (4 Si-C bilayers = 4H-SiC repeat distance) step features are clearly revealed around screw dislocation core. AFM image of SiC epilayer growth showing step bunching

4. ELECT 871 12/01/03 SiC devices: Comparison with GaN Mostly used for high power microwave devices (L, S, C-band amplifiers) Applications in high power and high temperature electronics (HEV circuits, engine sensors, power schottky and p-n diode rectifiers etc.) Advantages compared to GaN: –More mature technology than GaN –Bipolar devices (Thyristors, BJTs, DIMOS much more feasible) –Native substrate available, high thermal conductivity –Easier processing than GaN Disadvantages compared to GaN: –Indirect bandgap material, lower mobility, no HFET –Polytypism, even native substrates have large area defects –Expensive –Growth not easy due to high temperature process

5. ELECT 871 12/01/03 SiC based MESFETs Growth is easier due to lattice matched substrate. Also higher thermal conductivity. Have higher input and output impedances, so easier to design broadband matching networks Power output up to 6-7 W/mm Due to lower mobility of SiC F t usually not more than 20 GHz. (as 2DEG not possible) Acceptable noise figure and linearity Small periphery (2  300  m) 4H-SiC substrate (Vanadium doped) 0.25 μm p-type buffer layer Doping < 5  10 15 cm -3 0.26 μm n-type channel layer Doping ~2  10 17 cm -3 Layer structure

6. ELECT 871 12/01/03 SiC based power electronics 3100 V, 20 A, 62 kW-pulsed, single cell SiC Thyristors demonstrated Advantage of SiC is much higher power operation due to wider bandgap of SiC N + 4H-SiC Substrate N+N+ P+P+ P-P- N N JTE P+P+ N+N+ N+N+ Anode Gate Cathode 50  m, 7-9x10 14 cm -3 J3J3 Gate Anode 2 mm Asymmetrical gate turn off thyristor structure for SiC

7. ELECT 871 12/01/03 SiC based schottky diode gas sensors Devices made from wide bandgap materials such as SiC and GaN are sensitive to gases such as H 2, CO and NO 2. The basic mechanism for such sensing is that the schottky barrier height is lowered as the gas gets absorbed by the schottky barrier. Very useful for fire detection, and gas sensing in high temperature environment A SiC schottky diode for H 2 gas sensing

8. ELECT 871 12/01/03 Few final things The final is on 10 th December starting at 9.00 a.m. The presentation to be determined by alphabetical sequence of the Last Name (3 on Wednesday and 3 on Friday) Each presentation will be 15 minutes The project report is due by Friday morning, 12 th December (I need to submit grades by Friday). Good Luck!