Optical properties of small GaN-Al0.5Ga0.5N quantum dots grown on (11-22) GaN templates

Abstract

GaN/Al 0.5 Ga 0.5 N quantum dots deposited on the (11-22) plane have been grown by combining Molecular Beam Epitaxy (MBE) and Metal Organic Vapor Phase Epitaxy (MOVPE). The (11-22) GaN oriented template was realized by MOVPE starting from a M-plane oriented sapphire substrate. The average dot sizes are the following: between 15 and 20 nm in the and directions and a height ranging between 0.8 and 1.4 nm. Their density is ranging between 2 and 8x10 10 cm -2 . The crystal field splitting is measured in Al 0.5 Ga 0.5 N via polarized microphotoluminescence. We study the photoluminescence properties of small quantum dots which present innovative optical properties among which are the evolution of the polarization of the emitted photons at different temperatures. We also analyze the distortion of the photoluminescence at different time delays after the excitation pulse. A redshift is found that is attributed to the complex thermally-induced delocalization of the carriers through the assembly of dots from the smaller ones to the bigger ones.