Gallium Nitride Nanostructures Grown Directly on Silicon

Semiconductor nanostructures have attracted considerable attention recently because of their unique physical properties and potential uses in microelectronic and optoelectronic devices. Two-dimensional structures (wires) and three-dimensional structures (dots) have been successfully developed by either solution or vapor based methodologies. An important feature of these methods is the use of catalysts such as metal nanoparticles to grow novel systems such as carbon nanotubes or liquid metal droplets to grow metal nitrides and Si based elemental semiconductor materials. The metal particles and droplets are used to promote anisotropic crystal growth of the desired semiconductor system as bulk materials. In the nitride variety, for example, it has been reported that indium nitride (InN) growth is readily activated by a process in which nanometer size indium droplets serve as catalytic sites to form crystalline indium nitride free-standing fibers. This method is analogous to the vapor-liquid-solid (VLS) method that was used in the 60's and 70's to grow Si and Ge fibers by high temperature chemical vapor deposition. Researchers at Arizona State University have done considerable development on the formation of GaN islands on pure Si substrates. Previous work on the formation of GaN heterostructures on Si focused on the use of various types nucleation layers as well as seeded growth techniques such as lateral epitaxial overgrowth. This research group has now successfully prepared crystalline GaN directly on Si surfaces. Such nanostructures have attracted considerable attention recently because of their special physical properties and their potential application in microelectronic and optoelectronic devices. This process was realized by using newly synthesized sources for GaN, H2GaN3, and D2GaN3.