A Study of the Effect of V/III Flux Ratio and Substrate Temperature on the in Incorporation Efficiency in in_xGa_1−x/GaN Heterostructures Grown by Rf Plasma-Assisted Molecular Beam Epitaxy

Abstract

Laterally resolved high resolution X-ray diffraction (HRXRD) and photoluminescence spectroscopy (PL) have been used to assess In incorporation efficiency in In_xGa_1−xN/GaN heterostructures grown through rf-plasma-assisted molecular beam epitaxy. Average alloy composition over a set of In_xGa_1−xN/GaN superlattices has been found to depend systematically upon both substrate temperature (T_sub) and V/III flux ratio during growth. A pronounced thermally activated In loss (with more than an order-of-magnitude decrease in average alloy composition) is observed over a narrow temperature range (590–670°C), with V/III flux ratio fixed. Additionally, the V/III flux ratio is observed to further strongly affect In incorporation efficiency for samples grown at highT_sub, with up to an order-of-magnitude enhancement in In content despite only a minor increase in V/III flux ratio. PL spectra reveal redshifts as In content is increased and luminescence efficiency which degrades rapidly with decreasingT_sub. Results are consistent with In loss arising from thermally activated surface segregation + surface desorption processes during growth.