(665d) Homo- and Hetero-Epitaxial Growth On Nanowire Substrates

Epitaxial growth on planar substrates has been pursued for creating single crystal layers of new materials. In many circumstances, hetero-epitaxy is employed due to the limited availability of native substrates. In many important materials systems, such heteroepitaxy onto planar substrates leads to phase segregation and misfit dislocations due to lattice mismatch-induced stresses and strain. On the other hand, it has been proposed that the epitaxial growth on nanowire substrates could alleviate problems associated with planar substrates due to the lower interfacial contact area and stress relaxation within nanowire substrates.

In this presentation, we will present the fundamental studies conducted to follow the growth dynamics on nanowire substrates. In particular, the case of ternary alloy (In_xGa_1-xN) synthesis on to GaN and ZnO nanowire substrates will be discussed. Ternary In_xGa_1-xN alloys are promising materials for a variety of opto-electronic devices, photovoltaicsand photoelectrochemical systems owing to composition dependent tunability of the band gap from ultraviolet to near infrared. Specifically, the In_xGa_1-xN alloys with indium composition from 45-65 % can have the right band gap between 1.7-2.2 eV necessary for photoelectrochemical water splitting applications. We also present a discussion on the mechanism of the unique growth modes observed for both ternary alloys (In_xGa_1-xN) and GaN growth on “a” and “c” plane oriented GaN nanowires.