GaN quantum dot polarity determination by X-ray photoelectron diffraction

Abstract

Growth of GaN quantum dots (QDs) on polar and semipolar GaN substrates is a promising technology for efficient nitride-based light emitting diodes (LED) due to suppressed dislocation density in the active region of the devices. The QDs crystal orientation typically repeats the polarity of the substrate. In case of non-polar or semipolar substrates, the polarity of QDs is not obvious. In this article, the polarity of GaN QDs and of underlying layers was investigated nondestructively by X-ray photoelectron diffraction (XPD). Polar and semipolar GaN/Al 0.5 Ga 0.5 N heterostructures were grown on the sapphire substrates with (0001) and (1100) orientations by molecular beam epitaxy (MBE). Polar angle dependence of N 1s core-level photoelectron intensities were measured from GaN QDs and compared with the corresponding experimental curves from freestanding GaN crystals. It is confirmed experimentally, that the crystalline orientation of polar (0001) GaN QDs follows the orientation of the (0001) sapphire substrate. In case of semipolar GaN QDs grown on (1100) sapphire substrate, the (1122) polarity of QDs was determined.

Formation of spherical-shaped GaN and InN quantum dots on curved SiN/Si surface

“…That is, the structural properties of the III-nitride QDs reported in previous studies are insufficient to obtain 0D properties. Recently, alternative approaches such as inserting a strain-relieving layer, AlGaN or AlN, between a QD layer and a sapphire (or Si) substrate were proposed to decrease the difference in lattice mismatch to control the QD formation [12][13][14]. Xiao et al reported the improvement in the structural properties of InGaN QDs by adopting a quantum-sizecontrolled photo-electrochemical process [4].…”