GaN growth via tri-halide vapor phase epitaxy using solid source of GaCl₃: investigation of the growth dependence on NH₃ and additional Cl₂

Abstract

Gallium nitride (GaN) growth via a tri-halide vapor phase epitaxy method using a solid source of GaCl3 and gaseous NH3 was investigated both on Ga-polar and N-polar GaN templates. The relationship between gallium precursor molecule and growth polarity was clarified; it was found that a small amount of GaCl3 could be reduced by H2 originating from the decomposition of NH3 to produce GaCl, and additional Cl2 could suppress the reduction process. Accordingly, GaCl3 was found to be a proper Ga precursor for N-polar GaN growth, whereas GaCl was the proper precursor for Ga-polar GaN growth. The state of the Ga precursor molecule could be predicted by thermodynamic analysis. Furthermore, the decomposition ratio of NH3 could be determined by a combination of the experimental results and the calculated value of the thermodynamic analysis.

Suppression of cluster formation in GaN growth by tri-halide vapor phase epitaxy with external GaCl3 gas supply system

“…One is vaporization of solid GaCl 3 , which has a high vapor pressure (4500 Pa at 100 °C), and a high flow rate can be easily obtained. Several groups including ours [29][30][31] have reported high-speed growth of GaN with rates of about 10-50 μm h −1 by this method. Another method is the synthesis of GaCl 3 by the reaction of metallic gallium with Cl 2 gas.…”

“…Cluster formation is also important during VPE growth of GaN. 30) Especially in THVPE with an external precursor gas supply system, a highly concentrated precursor gas can be provided. It is important to increase the growth rate; however, this also results in cluster formation.…”

Effect of H2 addition on growth rate and surface morphology of GaN(0001) grown by halide-vapor-phase epitaxy using GaCl3

“…22,23) Other groups have also succeeded in the growth of GaN (000 1 ¯) using GaCl 3 . [24][25][26][27][28] On the other hand, it was reported that the growth rate on Ga-polar GaN(0001) using GaCl 3 is very low (almost zero). 26) This can be explained by unstable chemisorption of GaCl 3 molecules on nitrogen atoms on the (0001) surface because of the steric barrier created by the first chemisorbed GaCl 3 molecules.…”

“…Recently, Takekawa et al reported an increase in the HVPE growth rate for GaN(0001) using GaCl 3 by increasing the partial pressure of NH 3 . 28) They speculated that GaCl 3 is converted to GaCl by H 2 (GaCl 3 + H 2 → GaCl + 2HCl) generated from the decomposition of NH 3 . It is well known that GaN can be grown using GaCl on a (0001) surface.…”

“…We first investigated the effect of the NH 3 gas flow rate following a previous report by Takekawa. 28) We then studied the effect of H 2 addition on the growth rate, surface roughness and crystal quality.…”