Growth of Te on As-exposed Si(211): Electronic structure calculations Bikash C. Gupta, Inder P. Batra, and S. Sivananthan Department of Physics, 845 West Taylor Street, University of Illinois at Chicago, Chicago, Illinois 60607-7059, USA Received 24 June 2004; revised manuscript received 15 November 2004; published 28 February 2005 Electronic structure calculations are performed to obtain energetically favorable As-exposed Si211 and Te adsorbed As-exposed Si211 surfaces. Arsenic-exposed Si211 may be obtained by adsorbing As on Si211 or by replacing surface Si atoms by As. First, we carry out systematic investigations to obtain stable As- exposed Si211 due to As adsorption at various coverages. We find that at 1/2 monolayer ML coverage of As, the highly terraced Si211 surface becomes flat decorated with parallel As chains extending along the 011 ¯  direction. At 1 ML coverage the Si surface essentially retains its ideal structure with an added layer of As. Motivated by the adsorption sequence in the HgCdTe MCT growth on Si, Te adsorption on such an As-exposed Si211 is studied and 1/2 ML of Te coverage is found to be energetically feasible. Next, we explore a stable As-exposed Si211 upon replacement of surface Si atoms by As. An energetic comparison reveals that the As-exposed Si211 obtained by replacing surface Si atoms with As is more favorable com- pared to that obtained by adsorbing As on Si211. In line with the adsorption sequence in the MCT growth on Si, Te is then adsorbed on the most favorable As-exposed Si211 and in contrast to the earlier situation, Te coverage here is found to be 1 / 4 of ML which agrees with the experiment. DOI: 10.1103/PhysRevB.71.075328 PACS numbers: 73.90.+f, 68.90.+g I. INTRODUCTION As technological devices are often developed on Si sub- strates, Si surfaces continue to be a subject of intense theo- retical and experimental studies. Extensive investigations have been done on the low index Si surfaces, for example, Si001 and Si111. 1,2 Most of the theoretical investigations have been confined to low index surfaces due to the “sim- plicity” of the surface. However, the high index surfaces, Si211, Si311, Si331, Si557, and Si553, have at- tracted some attention recently. 3–19 High index surfaces play a technologically important role as substrates for the fabrica- tion of long wavelength infrared detectors 6–9 and as sub- strates for the formation of metallic nanowires. 12–14 Many of the high index Si surfaces are complicated in structure due to the existence of terraces and steps. The sur- face of interest here is Si211 which can be looked upon as stepped arrangement of narrow 111 terraces. A three- dimensional view of a small portion of the ideal Si211 surface is shown in Fig. 1. The atoms marked T called the terrace atoms on the terrace are threefold coordinated and thus have one dangling bond each; those on the step edge, marked E called the edge atoms are twofold coordinated and have two dangling bonds each. Atoms in the second layer and closest to the edge atoms are denoted as Tr called the trench atoms have one dangling bond each. The Si211 surface consists of two-atom wide terraces between terrace and edge atoms along the 1 ¯ 11 direction. Two consecutive terraces are separated by steps and are 9.4 Å apart in the 1 ¯ 11 direction, while they extend infinitely along 011 ¯ . The Si211 surface is now one of the surfaces of choice for epitaxial growth of polar both III-V and II-VI semicon- ductors on Si. It has been shown earlier 15 that the Si211 surface leads to a better quality epitaxial growth of GaP as compared to Si001 because it satisfies both the require- ments of interface neutrality and offering inequivalent favor- able binding sites for Ga and P. The Si211 surface has atoms with both one and two dangling bonds. The atoms with two dangling bonds can accommodate P, whereas Ga binds with Si211 that has a single dangling bond. Large area high quality CdTe layers have also been grown on the Si211 surface for subsequent growth of HgCdTe. 6–8 In par- ticular, our motivation for studying Si211 is due to emerg- ing experimental interest in epitaxial growth of HgCdTe after a successive growth of ZnTe and CdTe on the As-exposed surfaces aiming at the development of large area focal plane arrays for the fabrication of detectors. 9 As far as the reconstruction of Si211 is concerned there have been several studies. 16–19 However, a recent study by Baski et al. 10,11 was conclusive where the authors showed in their scanning tunneling microscopy images that the clean Si211 is unstable and it consists of nanofacets with 111 and 337 orientations. As there is evidence 12 that the 211 orientation is regained due to metal adsorption on Si211, we will use the bulk terminated surface to study the As ad- sorption on Si211. In addition, we will extend our study to understand the atomic configurations of Te on the As- exposed Si211. It has been established in recent experiments 9,20 that the epitaxial growth of II-IV materials on an As terminated Si surface gives a better quality film compared to that on a bare Si surface. For example, a high quality interface and better ZnS films were obtained 20 with As-exposed Si001. A better quality HgCdTe MCT growth is possible after a successive growth of ZnTe and CdTe on the As-exposed Si111 and Si211 surfaces. 9,21 So far, we do not have a comprehensive understanding of the interaction and atomic configuration of As on the Si211 surface. We therefore carry out extensive electronic structure calculations for As adsorption on the Si211 surface at various coverages. Here we note that an earlier study 19 to understand the interaction of As on Si211 revealed important results but was incomplete. There are PHYSICAL REVIEW B 71, 075328 2005 1098-0121/2005/717/0753288/$23.00 ©2005 The American Physical Society 075328-1