Low Temperature Deposition and Characterization of N- and P-Type Silicon Carbide Thin Films and Associated Ohmic and Schottky Contacts.
Abstract
Exposure of heated 6H-SiC wafers to SiH4 contained both in a gas stream and an activated plasma was investigated for low temperature SiC cleaning and oxygen removal prior to thin film deposition. UPS revealed the first observation of surface states on the cleaned 6H-SiC surface. Monocrystalline epitaxial films of Beta(3C)-SiC(111) and alpha(6H)-SiC(0001) were grown on vicinal (approx. 3.50 deg off(0001) towards) alpha(6H)-SiC(0001) substrates via gas-source MBE from 1050 to 1250 deg C using Si2H6 and C2H4. Undoped films were n-type; p-type films were achieved using Al evaporation during growth. The undoped 3C-SiC films grown on thin AIN buffer layers had carrier concentrations as low as 3x10( exp15/cu cm). Extremely efficient activation of n-type (Al) dopants has been achieved. Initial attempts at n-type doping using NH3 are also described. Surfaces of 6H-SiC(0001) homoepitaxial layers deposited on vicinal and on-axis 6H-SiC wafers by CVD have also been investigated using ultra-high vacuum scanning tunneling microscopy (UHV STM). The vicinal surface showed strongly undulating step configurations. The on-axis surface possessed much wider terraces and much smoother step undulations. Step heights on both surfaces were ^2.5 A corresponding to a single bilayer containing one Si and one C layer. After annealing at T>110 deg C for 3-5 min. in UHV. selected terraces contained honeycomb-like regions most likely caused by the transformation to graphite as a result of Si sublimation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1994
- Accession Number
- ADA289107
Entities
People
- Robert F Davis
- Robert J. Nemanich
Organizations
- North Carolina State University