Mizoguchi Hiroshi, Park Sang-Won, Katase Takayoshi, Yu Jiahao, Wang Junjie, Hosono Hideo
International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS)RINGGOLD, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
Inorg Chem. 2022 Jul 11;61(27):10359-10364. doi: 10.1021/acs.inorgchem.2c00884. Epub 2022 Jun 28.
Tetrahedral semiconductors such as Si adopt a diamond-type crystal structure with low packing density arising from open cavities in the crystallographic space. By taking LiAlGe as an example, we propose a zincblende-type framework as a platform for semiconductors possessing electroactive cavities. LiAlGe adopts a half-Heusler-type crystal structure including an ordered diamond-type sublattice (zincblende-type) (AlGe) and is an indirect semiconductor with a band gap of ∼0.1 eV. The conduction band minimum (CBM) is uniquely located at the cavity space surrounded by four cations (Al) in real space. The bond ionicity and cation (Al) p orbitals located around the Fermi energy are requisite for the CBM to float in the cavity space. DFT calculations indicate the conversion of the semiconductor to a semimetallic electride under a pressure of ∼8 GPa, which is accompanied by band gap collapse due to electron transfer from valence band maximum to the cavity space. The high-pressure electride of LiAlGe formed under a very small critical pressure is derived from the presence of inherent crystallographic cavities having deep orbital levels energetically. This finding suggests the possible utilization of electroactive cavity spaces in tetrahedral semiconductors, which are widely used in modern electronic devices.
诸如硅之类的四面体半导体采用金刚石型晶体结构，由于晶体学空间中的开放空洞，其堆积密度较低。以LiAlGe为例，我们提出一种闪锌矿型框架作为具有电活性空洞的半导体的平台。LiAlGe采用半赫斯勒型晶体结构，包括一个有序的金刚石型子晶格（闪锌矿型）（AlGe），是一种间接半导体，带隙约为0.1 eV。导带最小值（CBM）在实空间中独特地位于由四个阳离子（Al）包围的空洞空间处。键离子性和位于费米能级附近的阳离子（Al）p轨道是CBM在空洞空间中漂浮所必需的。密度泛函理论（DFT）计算表明，在约8 GPa的压力下，该半导体转变为半金属电子化合物，这伴随着由于电子从价带最大值转移到空洞空间而导致的带隙崩塌。在非常小的临界压力下形成的LiAlGe高压电子化合物源于存在具有高能级深轨道的固有晶体学空洞。这一发现表明，在现代电子设备中广泛使用的四面体半导体中的电活性空洞空间可能具有实用性。
