Growth Temperature Effects on Deep-Levels in Si Grown by Low Temperature Molecular Beam Epitaxy
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Growth Temperature Effects on Deep-Levels in Si Grown by Low Temperature Molecular Beam Epitaxy Sung-Yong Chung,a) Paul R. Berger, a) b) Z-Q. Fang,c) and Phillip E. Thompsond) Department of Electrical Engineering, The Ohio State University, Columbus, OH 43210 b) Department of Physics, The Ohio State University, Columbus, OH 43210 c) University Research Center, Wright State University, Dayton, OH 45435 USA d) Naval Research Laboratory, Washington, DC 20375-5347 USA
a)
ABSTRACT Deep-level transient spectroscopy (DLTS) measurements were performed on Si:Sb and Si:B n+-p step junction diodes grown by LT-MBE at various growth temperatures. The trap density dependence on growth temperature decreases with increasing temperature. However, segregation and diffusion increase with increasing temperature. Electron traps, E1 (0.42-0.45eV) and E2 (0.257eV), and hole traps, H1 (0.38-0.41eV), were found in B-doped layer grown at 370°C, 420°C, 500°C, and 600°C. These traps have been characterized by their capture crosssection, activation energy level, and trap density. The origins of the dominating electron traps are hypothesized as the association with pure divacancy defects. E1 level can be assigned for singly negatively charged divacancy V(0/-) + α and E2 level for doubly negatively charged divacancy V(-2/-). INTRODUCTION Epitaxially grown Si, combined with SiGe alloys, is now widely used to realize nanometer and heterostructure devices such as heterojunction bipolar transistors (HBT) and more recently resonant interband tunneling diodes (RITD) [1]. SiGe devices are attractive to device engineers due to their compatibility to the existing silicon processes and superior performance. Device performance is adversely affected by the presence of defects, because their energy levels act as generation-recombination centers that can quench carrier lifetime and degrade device performance. Molecular beam epitaxy (MBE) has proven to be a good tool for producing highquality epitaxial layers under non-equilibrium growth conditions. Low temperature molecular beam epitaxial (LT-MBE) growth has been especially useful as device sizes scale down to a few nanometers in size. The overall amount of dopant concentrations achievable using epitaxial growth techniques is limited due to segregation and out-diffusion which become more pronounced at higher growth temperatures that are closer to equilibrium conditions. LT-MBE is a far-from equilibrium growth technique that minimizes segregation and diffusion. Thus, the investigation of defects in LT-MBE grown material can help to optimize the growth process for optimal device performance. An effective method to study the electrical characteristics of defects is through deep level transient spectroscopy (DLTS) [2]. The DLTS technique has been widely used in many forms since its inception in 1974, since it provides useful information on the deep levels, including activation enthalpy, capture cross-section, and density of defects or impurities. The aim of this paper is to present the characteristics of
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