Atomic Structure of Non-Basal-Plane SiC Surfaces: Hydrogen Etching and Surface Phase Transformations
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0911-B07-01
Atomic Structure of Non-Basal-Plane SiC Surfaces: Hydrogen Etching and Surface Phase Transformations Serguei Soubatch1, Wai Y. Lee1, Martin Hetzel1, Chariya Virojanadara1, Camilla Coletti2, Stephen E. Saddow2, and Ulrich Starke1 1 Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstr. 1, Stuttgart, 70569, Germany 2 Dept. of Electrical Engineering, University of South Florida, 4202 East Fowler Avenue, ENB118, Tampa, Florida, 33620-5350
ABSTRACT A-plane (11¹20) and diagonal cut (1¹102) and (¹110¹2) surfaces of 4H-SiC have been investigated using atomic force microscopy (AFM), low-energy electron di®raction (LEED), Auger electron spectroscopy (AES), X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM). After hydrogen etching the surfaces show large, °at terraces. On SiC(11 ¹20) steps down to single atomic heights are observed. On the diagonal cut surfaces steps run parallel and perpendicular to the [¹1101] direction, yet drastically di®erent morphologies for the two isomorphic orientations are found. All surfaces immediately display a sharp LEED pattern. For SiC(1¹102) and SiC(¹110¹2) the additional signi¯cant presence of oxygen in the AES spectra indicates the development of an ordered oxide. All three surfaces show an oxygen free, well ordered surface after Si deposition and annealing. A transformation between di®erent surface phases is observed upon annealing.
INTRODUCTION
The physical properties of silicon carbide (SiC) have made it an interesting candidate as semiconductor material for high power, high frequency and high temperature device applications with the ¯rst industrial products already available. An important factor for further developments is the improvement of the quality of SiC substrate material. Recently, non-basal planes have become more interesting for this purpose. The use of SiC(11¹20) for growth in alternating orientation with the c-axis direction has been proposed [1]. Yet, also substrates with diagonal orientation with respect to the hexagonal unit cell have been used for epitaxial growth and device manufacturing. In a completely di®erent approach, porous SiC has shown intriguing perspectives for a variety of possible applications. Several pore morphologies have been discovered, depending on the electrochemical etch conditions, doping an so on [2]. An important pore type found is a triangular shaped pore channel with surfaces inclined by about 62± with respect to the basal plane. In 4H-SiC these tilted pore edges correspond to a (¹110¹2)-surface orientation. This 4H-SiC(¹110¹2) surface and its isomorphic opposite, i.e. the 4H-SiC(1¹102) surface show interesting properties from a consideration of bulk truncated surfaces alone. In addition, the surface orientation is very close to SiC(3¹308), which has been used for growth experiments and device manufacturing [3].
(a)
(b) A
(1120)
c 02 )
B
(1100)
(1 1
C B A
a3
a1
a2
B
4H-SiC
¹ ¹ ¹ 2) ¹ planes within the 4HFigure 1: (a) Schematic orientation of the (1120), (1100) and (110 SiC struct
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