arXiv subjects

Zongjian Fan

Publications and source records attributed to Zongjian Fan.

3 recordsLinked to original sources

arXiv2020

In-situ grown single crystal aluminum as a non-alloyed ohmic contact to n-ZnSe by molecular beam epitaxy (MBE)

Novel ohmic contacts to n-ZnSe are demonstrated using single crystal Al films deposited on epitaxially grown ZnSe (100) by molecular beam epitaxy (MBE). Electron Backscatter Diffraction (EBSD) confirmed the single crystalline structure of the Al films. The (110)-oriented Al layer was rotated rotated 45$^\circ$ relative to substrate to match the ZnSe (100) lattice constant. The as-grown Al-ZnSe contact exhibited nearly ideal ohmic characteristics over a large doping range of n-ZnSe without any additional treatment. The contact resistances are in a range of 10$^{-3}$ $Ω$-cm$^{2}$ for even lightly doped ZnSe ($\sim$10$^{17}$ cm$^{-3}$). Leaky Schottky behavior in lightly doped ZnSe samples suggested Al-ZnSe formed a low barrier height, Schottky limit contact. In-situ grown Al could act as a simple metal contact to n-ZnSe regardless of carrier concentration with lower resistance compared to other reported contacts in literatures. The reported novel metallization method could greatly simplify the ZnSe-based device fabrication complexity as well as lower the cost

cond-mat.mtrl-sci↗

arXiv2020

Interface Studies of Molecular Beam Epitaxy (MBE) Grown ZnSe-GaAs Heterovalent Structures

Comprehensive investigations on ZnSe/GaAs and GaAs/ZnSe interfaces were carried out by photoluminescence (PL) and transmission electron microscopy (TEM), as a part of realizing high quality ZnSe-GaAs (100) hetero-valent structures (HS). The nature of ZnSe/GaAs interface under different surface terminations of GaAs was examined. The ZnSe/Ga-terminated GaAs was found to have a superior optical and microstructural quality, with a chemical interface consisting of a mixture of both the GaAs and ZnSe atomic constituents. For GaAs/ZnSe interface studies, a low-temperature migration enhanced epitaxy (LT-MEE) growth technique was used to grow GaAs layers under the conditions compatible to the growth of ZnSe. Both Ga and As-initialized LT-MEE GaAs/ZnSe interfaces were investigated. A defective transition layer was observed along the As-initialized GaAs/ZnSe interface, which may be attributed to the formation Zn$_3$As$_2$ compound. The correlation between the observed optical as well as structural properties of both the (GaAs/ZnSe and ZnSe/GaAs) interfaces and the growth conditions used in this study are discussed in detail. This study could provide a valuable insight on the interface nature of ZnSe-GaAs HS.

cond-mat.mtrl-sci↗

arXiv2017

Transition between strong and weak topological insulator in ZrTe$_5$ and HfTe$_5$

ZrTe$_5$ and HfTe$_5$ have attracted increasingly attention recently since the theoretical prediction of being topological insulators (TIs). However, subsequent works show many contradictions about their topological nature.Three possible phases, i.e. strong TI, weak TI, and Dirac semi-metal, have been observed in different experiments until now. Essentially whether ZrTe$_5$ or HfTe$_5$ has a band gap or not is still a question. Here, we present detailed first-principles calculations on the electronic and topological properties of ZrTe$_5$ and HfTe$_5$ on variant volumes and clearly demonstrate the topological phase transition from a strong TI, going through an intermediate Dirac semi-metal phase, then to a weak TI when the crystal expands.Our work might give a unified explain about the divergent experimental results and propose the crucial clue to further experiments to elucidate the topological nature of these materials.

cond-mat.mtrl-sci↗