Relationship Between Interface Structure and Schottky Barrier Height
- PDF / 551,043 Bytes
- 9 Pages / 414.72 x 648 pts Page_size
- 58 Downloads / 238 Views
ABSTRACT The clear dependence of the Schottky barrier height (SBH) on the structure of a metalsemiconductor (MS) interface is described for a few high-quality epitaxial MS systems. Polycrystalline MS interfaces, for which such a dependence is often absent, are shown to display clear evidence for SBH inhomogeneity, in direct conflict with the Fermi level (FL) pinning concept they helped to create. Recent theoretical calculations show that many basic tenets of the interface state pinning models are unfounded. The redistribution of charge as a result of bonding at the MS interface seems to be the most important contribution to the interface dipole and, hence, the SBH.
INTRODUCTION MS interfaces are vitally important to all electronic and optoelectronic devices. Despite the great strides which were made in the past several decades in explaining many fundamental condensed matter phenomena and in the processing of complicated structures on semiconductors, the explanation of the Schottky barrier (SB) at MS interfaces has remained at the stage of speculation.[11 It has long been thought that the formation mechanism of the SBH may be revealed by studying whatever correlation(s) one may find between the SBH's experimentally observed from many MS systems and some, usually bulk-related, parameter(s) (e.g. Fig. 3 below). The most notable result of such practices, the observation of the lack of a strong dependence of the SBH on the metal work function, has been interpreted to suggest that the interface FL is pinned by a high density of localized states in the bandgap.111 Surface states,[2' defect states, 131 [41 and metal induced gap states (MIGS) 15' 161have all been conjectured to be responsible for FL pinning. If the FL were pinned, the SBH would not depend on the structure of the MS interface and the SBH should be uniform at any MS interface. Until very recently, the SBH has always been assumed to be uniform at a MS interface, even though the validity of this assumption has never been established on a general basis. Since the local bonding and structure determine the redistribution of charge and, therefore, the electric dipole across a MS interface, it is only natural to expect that the interface structure should have a significant influence on the formation of the SBH. FL pinning theories propose that screening by a high density of interface states damps out this effect of interface structure. Therefore, it seems that a first step toward solving the SB mystery is to answer the question of whether a strong relationship exists between the structure and the SBH of a MS interface. In this paper, we will show that a causal relationship indeed exists between the structure and the SBH. The redistribution of charge as a result of bonding at the MS interface seems to be the most important contributor of the interface dipole and, hence, the SBH.
Mat. Res. Soc. Symp. Proc. Vol. 318. ©1994 Materials Research Society
CORRELATION OF SBH WITH STRUCTURE: EPITAXIAL MS INTERFACES Ordinary MS interfaces consist of a host of different stru
Data Loading...
