Systematic study of effects of growth conditions on the (nano-, meso-, micro)size and (one-, two-, three-dimensional) shape of GaN single crystals grown by a direct reaction of Ga with ammonia

Abstract

A series of experiments have been conducted to systematically study the effects of growth conditions (NH3 flow rate, growth temperature, chamber pressure, and growth location) on the size (nano, meso, or micro) and the shape (one, two, or three dimensional) of GaN single crystal products grown by a direct reaction of Ga with NH3. A growth map with a wider range of experimental parameters was developed; it has three distinct zones. The size and shape of the products in every zone were found to depend on both temperature and NH3 flow rate with other growth conditions fixed. An effective surface diffusion length consisting of the Ga atomic surface diffusion length and the GaN molecular surface diffusion length, and the anisotropy of the Ga surface diffusion length and the GaN growth rate in different growth directions were introduced into the growth model, in such a way that it allowed successful explanation of all observed results. The optimal growth parameters could thus be determined, which conclusively demonstrated that nanowires with uniform diameter, clear crystal structure, length larger than 1 mm, uniform location distribution, and high yield can be obtained. Such a growth map based on in-depth understanding of the growth mechanism provides a clear direction for growing various materials with desired size and shape.

Fabrication of GaN-based nanoscale device structures utilizing focused ion beam induced Pt deposition

“…Ammonia (~99.999% pure) was introduced at a rate of 50 SCCM-100 SCCM (SCCM denotes cubic center per minute at STP), with the growth temperature set between 850 °C and 900 °C for 3 h-4 h. Depending on the growth temperature and reactor pressure, lengths and diameters of these nanowires can be varied. 9 The growth results in a matrix on the boron nitride boat and quartz liner, containing single crystal GaN nanowires together with GaN platelets. After completion of the growth, the GaN matrix with nanowires was collected from the inner lining of the furnace, and then sonicated in isopropanol to achieve a dilute suspension of nanowires.…”

“…As a result nanostructures and nanodevices made from GaN and related nitrides have great potential for realizing next generation efficient nanoscale UV/visible light emitters, detectors, and high temperature electronic devices. Although significant progress has been made in semiconducting nanowire growth, 6,7,8,9 further optimization of the growth processes is still required. Positioning them on a suitable substrate for device fabrication often involves complex aligning procedures such as electric field assisted aligning, 5 microfluidic aligning, and chemical patterning.…”

Internal structure of multiphase zinc-blende wurtzite gallium nitride nanowires

“…The multiphase nanowire structures reported here incorporate highly crystalline zinc-blende and wurtzite phases simultaneously that extend in the longitudinal direction along the entire length of the nanowire [14]. The nanowires were synthesized in a quartz tube furnace at 850 • C in a direct reaction of gallium vapor and flowing ammonia (NH 3 ) [15][16][17]. Plain-view HRTEM (JEOL 2200FS, 200 kV) investigations of over 30 nanowires showed that the zinc-blende/wurtzite multiphase nanowires were consistently obtained using this growth method [18].…”

Electronic and Structural Characteristics of Zinc-Blende Wurtzite Biphasic Homostructure GaN Nanowires

“…The nanowires form a single seamless structure along well defined crystal axes. A study of the temperature-composition parameter space provides a predictive model for nanowire growth 12 . Scanning electron microscopy (Hitachi S-4700-II FESEM) images of the as grown GaN nanowire/amorphous/platelet matrix and the nanowire from platelet growth are shown in Figure 1(A,B).…”