Synchrotron X‐ray investigation of La_0.3Sr_0.7Al_0.65Ta_0.35O₃ crystals

Abstract

The La 0.3 Sr 0.7 Al 0.65 Ta 0.35 O 3 (LSAT) substrates were studied with a number of X-ray diffraction methods exploring both synchrotron white and monochromatic beam. The observation of selective etching patterns was performed in neighbouring samples. White beam back-reflection projection topographs revealed only the segregation fringes around the central core and a delicate grain-like structure. The most important for verification of dislocation presence were the transmission projection and section topographs. These topographs also did not reveal any images of extended dislocation but only the growth bands and tiny grainlike structure. The section topographs provided some details of paroboloidal growth surface inside the crystal. It may be concluded that the investigated crystal probably contains small coherent inclusions responsible for the etch pits and the mentioned grain-like structure. The synchrotron rocking curves revealed a number of maxima, which might be attributed to the regions with different lattice parameter, connected with segregation fringes. The sequence of maxima was different for different regions of the sample.

Achieve high-quality GaN films on La0.3Sr1.7AlTaO6 (LSAT) substrates by low-temperature molecular beam epitaxy

“…It has a cubic unit cell with lattice parameter a = 7.730 Å. 8,9 The lattice mismatch for LSAT (111) plane with GaN c-plane is only about 1%, which is much smaller than that for sapphire. In addition to its smaller lattice mismatch with nitrides, LSAT shares the same cleavage direction with c-plane nitrides, which obviously gives an advantage during device fabrication.…”