Abstract
Three-dimensional (3D) GaN is a III-V compound semiconductor with potential optoelectronic applications. In this paper, starting from 3D GaN in wurtzite and zinc-blende structures, we investigated the mechanical, electronic, and optical properties of the 2D single-layer honeycomb structure of GaN () and its bilayer, trilayer, and multilayer van der Waals solids using density-functional theory. Based on high-temperature ab initio molecular-dynamics calculations, we first showed that can remain stable at high temperature. Then we performed a comparative study to reveal how the physical properties vary with dimensionality. While 3D GaN is a direct-band-gap semiconductor, in two dimensions has a relatively wider indirect band gap. Moreover, 2D displays a higher Poisson ratio and slightly less charge transfer from cation to anion. In two dimensions, the optical-absorption spectra of 3D crystalline phases are modified dramatically, and their absorption onset energy is blueshifted. We also showed that the physical properties predicted for freestanding are preserved when is grown on metallic as well as semiconducting substrates. In particular, 3D layered blue phosphorus, being nearly lattice-matched to , is found to be an excellent substrate for growing . Bilayer, trilayer, and van der Waals crystals can be constructed by a special stacking sequence of , and they can display electronic and optical properties that can be controlled by the number of layers. In particular, their fundamental band gap decreases and changes from indirect to direct with an increasing number of layers.
4 More- Received 2 December 2015
DOI:https://doi.org/10.1103/PhysRevB.93.085431
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