Defects and Impurities in 4H- and 6H-SiC Homoepitaxial Layers: Identification, Origin, Effect on Properties of Ohmic Contacts and Insulating Layers and Reduction
Abstract
Chemical vapor deposition systems are being fabricated to deposit 4H- and 6H-SiC thin films at moderate and very high temperatures. Single crystalline A1N films with smooth surfaces were grown using gas-source MBE and characterized with RHEED, XRD, TEM and SIMS. The C-V characteristics of All A1N/SiC heterostructures depended strongly on temperature from 200 to 573 K and exhibited hysteresis effects consistent with the presence of slow interface traps. The A1N/SiC interface had a density of trapped negative charge of 3x10(exp 11)/sq cm at 27 deg C; it decreased with increasing temperature. A three-step process involving surface preparation, initial insulator formation, and oxide deposition was developed for investigation of oxide growth on 6H- and 4H-SiC. Films of SiO2 have been deposited at approx. 10 A/min for characterization. Measured impact ionization coefficient data indicate that the reverse breakdown voltage of 6H- and 4H-SiC devices should increase with temperature. This data shows that Baliga's figure of merit increases by approx. 1.5 and approx. 1.8 for 6H- and 4H-SiC, respectively, indicating superior specific on resistance for SiC field effect transistors relative to that projected earlier. Electron inversion layer mobilities of 110 sq cm/Vs (the highest reported to date) and 160 sq cm/Vs (the first reported value) have been measured in 6H- and 4H-SiC lateral MOSFETs. The devices were fabricated using a non-selfaligned process. A low temperature deposited oxide (LTO) subjected to different oxidizing and inert anneals was used as the gate dielectric.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1997
- Accession Number
- ADA328450
Entities
People
- Bayant Jayant Baliga
- M. O. Aboelfotoh
- Robert F Davis
- Robert J. Nemanich
Organizations
- North Carolina State University