Reduction of carbon impurities in GaN grown by MOCVD using an NH3-plasma source

In this work, we demonstrate GaN epitaxial growth by plasma-enhanced metalorganic chemical vapor deposition (MOCVD) using trimethylgallium [TMGa, Ga(CH3)3] and ammonia (NH3). Impacts of TMGa, NH3 molar flow rates, and plasma power on surface morphologies and carbon residual impurity concentrations in GaN epitaxial layer have been clarified. GaN surfaces showed step and terrace structures under a wide range of TMGa and NH3 molar flow rates. The residual carbon atomic concentrations in GaN epitaxial layers are found to be remarkably reduced by using NH3-plasma. The electrical characteristics of AlGaN/GaN-based high electron mobility transistor structure exhibits a lower sheet resistance when NH3-plasma is applied. This is mostly owing to the reduction in carbon residual impurities, which act as electron traps. The plasma MOCVD enables reduction in NH3 consumption or increase in GaN growth rate by 50%, which leads to enhancement of manufacturing productivity.