Strong anisotropy and layer-dependent carrier mobility of two-dimensional semiconductor ZrGeTe4

Layered ZrGeTe4 is a new type of ternary anisotropic semiconductor. The strong in-plane anisotropy may give us another degree of freedom for controlling electrical and optical properties, and designing advanced nanodevices. Using first-principles calculations, physical properties such as band structure, phonon vibration, and carrier mobility of layered ZrGeTe4 from bulk to monolayer were investigated. The bulk and few-layer ZrGeTe4 are predicted as indirect bandgap semiconductors, but the monolayer ZrGeTe4 turns out to be a direct band gap semiconductor with moderate value of 1.08 eV. Electronic structure calculations reveal that the van der Waals interaction is the main reason of causing the transition from indirect band gap to direct one. Phonon calculations demonstrate that the layered ZrGeTe4 is mechanically stable and anisotropic. In orders of magnitude, the predicted average carrier mobility of ZrGeTe4 (∼103 cm2 V−1 s−1) is between that of graphene (∼105) and MoS2 (∼102), and the anisotropy of electronic mobility is similar to that of black phosphorus, while hole mobility varies with the numbers of layers.