Room-temperature nonradiative recombination lifetimes in c-plane Al1−xInxN epilayers nearly and modestly lattice-matched to GaN (0.11 ≤ x ≤ 0.21)

Abstract

Lattice-matched Al1− xIn xN / GaN heterostructures with InN mole fraction ( x) of 0.18 have attracted considerable interest for use in GaN-based optoelectronic devices. Because the light emission efficiency ([Formula: see text]) of Al1− xIn xN alloys is far less than that of In xGa1− xN, understanding its causes is essential. For this purpose, room-temperature photoluminescence lifetime ([Formula: see text]), which almost represents the nonradiative recombination lifetime that limits the internal quantum efficiency in low [Formula: see text] semiconductors, of c-plane Al1− xIn xN epilayers nearly and modestly lattice-matched to GaN ([Formula: see text]) was examined. For the epilayers grown on low threading dislocation density (TDD) GaN substrates ([Formula: see text]), [Formula: see text] principally decreased with increasing x, indicating a progressive increase in the concentration of nonradiative recombination centers (NRCs), [Formula: see text]. One of the probable causes is the growth temperature ([Formula: see text]) reduction that is indispensable to incorporate more In, because in insufficient [Formula: see text] regime higher [Formula: see text] is preferred for enhancing the surface migration of adatoms to decrease the concentrations of vacancies that compose NRCs. The Al1− xIn xN epilayers of the same x but grown on high TDD ([Formula: see text]) GaN-on-sapphire templates exhibited shorter [Formula: see text]. Because the diffusion length of minority carriers was nearly zero in the Al1− xIn xN epilayers, the shorter [Formula: see text] indicates higher bulk [Formula: see text] in high TDD epilayers. The Al1− xIn xN epilayers of considerably rough surface morphologies exhibited spatially inhomogeneous [Formula: see text], implying that excited carriers recombined everywhere at InN-rich to InN-poor portions, where [Formula: see text] were likely lower to higher, respectively, than the average due to the deviations in the surface stoichiometry at various non- c-plane surfaces at a given [Formula: see text].