Effects of Deposition Conditions of First InSb Layer on Electrical Properties of n-Type InSb Films Grown With Two-Step Growth Method via InSb Bilayer Sara Khamseh  , Yuichiro Yasui 1 , Koji Nakayama 1 , Kimihiko Nakatani 1 , Masayuki Mori 1 , and Koichi Maezawa 1 Venture Business Laboratory, University of Toyama, Toyama 930-8555, Japan 1 Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan Received September 13, 2010; accepted November 15, 2010; published online April 20, 2011 The n-type InSb films were prepared on Si(111) substrates with a two-step growth method via an InSb bilayer. This growth method consists of an initial low-temperature InSb layer growth and a subsequent high-temperature InSb layer growth. In order to obtain a heteroepitaxial InSb film with a high electron mobility, the growth conditions of the first InSb layer were optimized. The first InSb layer was prepared at higher growth temperatures. Moreover, the thickness of the first InSb layer with a lower crystalline quality and poor electrical properties decreased. InSb films prepared with new deposition conditions showed a higher crystalline quality, a lower defects density, and better electrical properties than the films indicated in our previous report. An InSb film with a high electron mobility of 38,000 cm 2 /(VÁs) which shows a high potential for new high-speed device applications was obtained. # 2011 The Japan Society of Applied Physics 1. Introduction InSb is a narrow-gap semiconductor with a low effective mass and possesses the highest electron mobility among III–V compound semiconductors. Due to these excellent electronic characteristics, InSb has received a great deal of attention as a good candidate for infrared detectors, high- speed devices and magnetic sensors. 1–4) The heteroepitaxial growth of InSb on Si has attracted much interest from the viewpoint of integration of InSb-based devices and Si-LSI. However, the heteroepitaxy of InSb on Si is difficult to achieve because of the large lattice mismatch of about 19.3% between them. Two main methods are applied to solve this problem. In the first method, various buffer layers, such as GaAs and Ge, have been used. 5–8) In the second method, the surface reconstructions by In and Sb atoms are formed on Si substrates at the initial growth stage. 9–12) It has been shown that the use of a suitable reconstructed surface by In and Sb atoms is a good technique for solving the lattice mismatch problem. 13,14) For instance, the use of an InSb bilayer, prepared by the adsorption of 1 monolayer (ML) Sb onto a surface reconstructed by In atoms, can be a good solution of the lattice mismatch problem. 13–16) The InSb films synthe- sized on the InSb bilayer were rotated 30  with respect to the Si(111) surface. In this case, the lattice mismatch between InSb and Si was nominally reduced to about 3.3%. Some groups reported that the two-step growth method is a successful way of growing highly mismatched systems, such as InSb/GaAs and InSb/Si. 17–19) This growth method consists of an initial low-temperature InSb layer growth (180–240  C) and a subsequent high-temperature InSb layer growth (350–440  C). In our previous studies, we investi- gated the growth of InSb films on the InSb bilayer by a two- step growth method. 20–22) In this method, the substrate was first held at 180–200  C to grow the first InSb layer to prevent the desorption of In atoms from the InSb bilayer. The low-temperature growth of the first InSb layer leads to a low crystalline quality. It is well known that the higher crystal- line quality in monocrystalline films results in narrower XRD-FWHM (X-ray diffraction full-width at half max- imum) values, which indicates larger crystal size in the films. With increasing crystal size, the number of grain boundaries and the density of grain boundary defects decrease. Then, the substrate temperature increases to 350  C for the growth of the second InSb layer. 20–22) The growth temperature of the second InSb layer is also restricted owing to the degradation of the first InSb layer at higher temperatures. The room- temperature electron mobility of InSb films prepared with this method ranged from 18,000 to 20,000 cm 2 /(Vs). 20–22) If we attempt to prepare an InSb film with better electrical properties, it is necessary to improve its crystalline quality. To synthesize an InSb film with a higher crystalline quality and better electrical properties, it is necessary to increase the growth temperature. However, as mentioned above, there are some restrictions for high-temperature growth of an InSb film when we use an InSb bilayer. In our previous study, we prepared an InSb film with a high crystalline quality and good electric properties by gradually increasing the growth temperature of the second InSb layer during deposition. 15) Accordingly, in our current study, we tried to improve the crystalline quality of the first InSb layer, by gradually increasing its growth temperature. Moreover, the thickness of the first InSb layer with a low crystalline quality and poor electric properties decreased compared with that indicated in our previous reports. The microstructure and electrical pro- perties of InSb films were compared with our previous data. 2. Experimental Procedure All the depositions were carried out in an OMICRON molecular beam epitaxy (MBE) chamber with a base pressure of about 2  10 8 Pa, equipped with a reflection high-energy electron diffraction (RHEED) system. The substrate with dimensions of about 15  4  0:6 mm 3 was obtained from a mirror-polished p-type Si(111) wafer with a resistivity of about 20 cm. The substrates were degassed at about 600  C for 12 h, followed by flush annealing at 1250  C, and then slowly cooled in the chamber. This process gave a clean (77) surface, as confirmed by RHEED. High-purity (6 N) elemental indium and antimony were used as source materials and evaporated from each PBN K-cell. The substrate temperature was monitored by an infrared pyrom- eter. Prior to the growth of InSb films, the InSb bilayer was prepared by the following process. First, a Si(111)– ffiffi 3 p  ffiffi 3 p -In surface phase was prepared by the deposition of 0.33 ML In atoms onto the clean Si(111)–77 surface at 450  C. After cooling down to RT, additional In atoms of  E-mail address: srkhamseh@yahoo.com Japanese Journal of Applied Physics 50 (2011) 04DH13 SS10016 114 Total pages 4 04DH13-1 # 2011 The Japan Society of Applied Physics REGULAR PAPER DOI: 10.1143/JJAP.50.04DH13