Microstructures, defects, and localization luminescence in InGaAsN alloy films

摘要

We studied the structural and optical properties of In_xGa_(1-x)As_(1-y)N_y (x = 0.116, ～0.3 and y = 0-0.031) alloy films grown by low-pressure metalorganic vapour epitaxy (LP-MOVPE), performing high-resolution transmission electron microscopy (HRTEM) and photoluminescece (PL) measurements. The effects of rapid thermal annealing (RTA) at 700 °C under N_2 ambient were also examined. The TEM images showed that with increasing In content, not only misfit dislocations near the InGaAsN/GaAs interface due to the large lattice mismatch with the GaAs subatrate, but also many defects in the InGaAsN layer due to the relaxation of local strain increased. From energy dispersive X-ray (EDX) analysis of the high In-content layers (x = 0.3-0.355), we found a significant In fluctuation in the InGaAsN layer. The PL peaks of In_(0.116)Ga_(0.884)As_(1-y)N_y (y = 0-0.031) measured at 7 K shifted to the high-energy side after RTA, while those of In_xGa_(1-x)As_(1-y)N_y (x = ～0.3, y = 0-0.015) shifted unusually to the low-energy side. This unsual behavior of the high In-content layer after RTA may be attributed to the enlargement of quantum-dot-like regions, which are formed by the compositional fluctuation in microscopic scale.