On mechanisms governing AlN and AlGaN growth rate and composition in large substrate size planetary MOVPE reactors

• Published in: Journal of crystal growth Vol. 393; pp. 103 - 107
• Main Authors: Dauelsberg, Martin, Brien, Daniel, Rauf, Hendrik, Reiher, Fabian, Baumgartl, Johannes, Häberlen, Oliver, Segal, Alexander S., Lobanova, Anna V., Yakovlev, Eugene V., Talalaev, Roman A.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2014; Elsevier
• Subjects: A1. Computer simulation; A3. Metal–organic vapor phase epitaxy; Aluminum; Ammonia; B1. AlGaN; B1. Nitrides; Ceilings; Desorption; Mathematical models; Partial pressure; Reactors; Temperature dependence; A1. Computer simulation; A3. Metal–organic vapor phase epitaxy; B1. Nitrides; B1. AlGaN
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2013.08.018

We report about a MOVPE parameter study carried out on a Planetary Reactor to determine factors that govern the incorporation efficiency of aluminum and gallium into AlxGa1−xN, hence its solid composition x and growth rate. Parameter variations include pressure, flow rate, wafer and ceiling temperature, V–III-ratio, and Al/(Al+Ga) inlet ratio. The target composition is 0.15<x<0.4. Losses of nutrients due to gas phase reactions between metalorganics and ammonia were suppressed by choosing operational conditions of low pressure and relatively low V–III ratios. The temperature dependence of composition x is instead accounted for by selective desorption of gallium from the layer surface which occurs independent of epitaxial growth and which aluminum is not subject to. The diminution of partial GaN growth rate in AlxGa1−xN due to this phenomenon is found to depend not only on temperature but also on ammonia partial pressure and the solid composition of AlxGa1−xN. The rate of growth rate reduction by this effect is determined quantitatively by comparing experimental growth data with modeling prediction of gallium incorporation computed by disregarding the desorption kinetics. Based on the obtained data the gallium desorption rate was found to follow an Arrhenius temperature dependence with an activation energy of Ea=2.1eV. •We present a parameter study of MOVPE grown AlGaN solid composition dependence.•AlGaN composition is affected by gallium desorption in the hydrogen–ammonia ambient.•The aluminum constituent is not subject to the same desorption kinetics.•The rate of gallium desorption depends on temperature, ammonia flow and Al-content.•The activation energy of gallium desorption is obtained as Ea=2.1eV.