Abstract
Critical dimensions for nanowire core-multishell heterostructures are analyzed by using finite-element method based on the energy equilibrium criteria. Results show that the nanowire core-shell heterostructure can sufficiently reduce the strain in the shell and increase the critical shell thickness. The critical dimensions for the nanowire core-multishell heterostructure are determined by the stress fields generated at two heterointerfaces. For thin barrier, the critical dimensions decrease as the core radius increases, while when the barrier is thick enough, the critical dimensions show an increase with the increase of core radius conversely. This can be attributed to a competition between the lattice mismatch and strain distribution, which dominate the critical dimensions alternatively. Two critical quantum well thicknesses are obtained in the nanowire core-multishell heterostructure. Below the dislocation-free critical thickness, the structure will be coherent regardless of the barrier thickness. While above the dislocation-unavoidable thickness, dislocations are always energetically favored. In the dislocation-controllable region between the two critical thicknesses, coherent structure can be obtained via controlling the well and barrier thicknesses. The results are in good agreement with the experimental data and may serve as guidance for the design of coherent nanowire core-multishell quantum well structures and devices.
Highlights
In recent years, semiconductor nanowires (NWs) have attracted great attention due to their potential applications in electronic and photonic devices such as field effect transistors, lasers, photodetectors, and solar cells [1,2,3,4]
The study on critical dimensions for NW core-multishell heterostructures has not been reported yet, which is significant for achieving high-performance optoelectronic devices
Critical Dimensions for the NW Core-Shell Heterostructure Figure 2 shows the distribution of stress field over the cross section of three GaAs/In0.2Ga0.8As NW core-shell heterostructures with a core radius and shell thickness of 50, 20 nm (a, b), 100, 20 nm (c, d), and 50, 100 nm (e, f ), respectively
Summary
Semiconductor nanowires (NWs) have attracted great attention due to their potential applications in electronic and photonic devices such as field effect transistors, lasers, photodetectors, and solar cells [1,2,3,4]. In comparison with homogeneous NWs, NW heterostructures can dramatically improve the performance and add advanced functionalities. In comparison with axial heterostructures, the strain release mechanism is quite different for core-shell heterostructures. The lateral stress relaxation effect, which can sufficiently reduce the strain in NW axial heterostructures, is negligible in NW core-shell heterostructures due to a large interface area [11]. Experiments on NW coreshell heterostructures have been widely reported [16,17,18,19,20,21], theoretical work on the critical dimensions of core-shell heterostructures is still limited [22,23,24,25]. The study on critical dimensions for NW core-multishell heterostructures has not been reported yet, which is significant for achieving high-performance optoelectronic devices. We explore the coherency limits in NW core-shell and core-multishell heterostructures by
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