Effect of substrate temperature and V/III flux ratio on In incorporation for InGaN/GaN heterostructures grown by plasma-assisted molecular-beam epitaxy

Abstract

Reflection high-energy electron diffraction (RHEED) and laterally spatially resolved high resolution x-ray diffraction (HRXRD) have been used to identify and characterize rf plasma-assisted molecular-beam epitaxial growth factors which strongly affect the efficiency of In incorporation into InxGa1−xN epitaxial materials. HRXRD results for InxGa1−xN/GaN superlattices reveal a particularly strong dependence of average alloy composition x̄ upon both substrate growth temperature and incident V/III flux ratio. For fixed flux ratio, results reveal a strong thermally activated behavior, with over an order-of-magnitude decrease in x̄ with increasing growth temperature within the narrow range 590–670 °C. Within this same range, a further strong dependence upon V/III flux ratio is observed. The decreased In incorporation at elevated substrate temperatures is tentatively attributed to In surface-segregation and desorption processes. RHEED observations support this segregation/desorption interpretation to account for In loss.