Transmission electron microscope studies on atomic structures of semiconductor heterovalent interfaces
Abstract
Heterovalent interfaces are interfaces between two materials with identical lattice structures but different electron configurations. Interfaces of GaAs/Ge, ZnSe/GaAs, and Ga$\sb2$Se$\sb3$/GaAs are examples of this type of interfaces. Because of the mismatch of electronic configurations, a variety of structural modifications may occur at the interfaces, depending on growth conditions of heterostructures. Studies on the atomic structure of the heterovalent interfaces may provide valuable information in understanding the chemical bonding of the interfaces, which is essential for the development of the semiconductor heterojunction devices. In this study, three heterovalent interfaces, ZnSe/GaAs, CdTe/InSb, and Ga$\sb2$Se$\sb3$/GaAs have been examined by utilizing transmission electron microscopy. The heterostructures were grown by using molecular beam epitaxy with control of surface conditions of the substrate epilayers. Two types of interface structure modifications were observed. One is the interface compound layer at II-VI/III-V interfaces, such as Ga$\sb2$Se$\sb3$ at ZnSe/GaAs interfaces and In$\sb2$Te$\sb3$ at CdTe/InSb interfaces. Another is the interface reconstruction at Ga$\sb2$Se$\sb3$/GaAs interfaces. The interface reconstruction is nearly two dimensional ordering with an ordered arrangement of vacancies in a Ga atomic plane to form c(2x2) lattice, that is, a half of the Ga sites in the interface reconstruction are vacant. The origin of these two types of interface structural modifications is examined with the emphasis on the role of the mismatch of electronic configurations.
Degree
Ph.D.
Advisors
Otsuka, Purdue University.
Subject Area
Materials science|Electrical engineering|Condensation
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