Determination of microdistortion components and their application to structural characterization of HVPE GaN epitaxial layers

Abstract

The dislocation structure of hydride vapour phase epitaxial thick GaN layers grown on sapphire is studied by analysis of the microdistortion tensor components. Symmetrical reflections (including reflections from planes forming large angles with the basal plane) with two modes of scanning (θ and θ-2θ) in two geometries (Bragg and Laue) are used to obtain the tensor components. The instant connections between the tensor components and major dislocation types are specified. Different types of dislocation distributions have been identified in the thick GaN films grown on sapphire without and with undoped and Si-doped metal-organic chemical vapour deposited templates.

Internal strains and crystal structure of the layers in AlGaN/GaN heterostructures grown on a sapphire substrate

“…10 An analysis of the XRD rocking curves in different geometries allows us to characterize the orientation distribution of the structural defects. 11 For the investigation of mosaic structures, it is particularly important to investigate the local three-dimensional ͑3D͒ distribution of a crystalline phase, the local texture and the deformation tensor with a spatial resolution below 1 m. The method of 3D XRD microscopy allows crystalline materials to be investigated with micrometer resolution, 12 and X-ray microdiffraction at high-power synchrotron excitation permits submicron resolution measurements of the deformation tensor in three directions. 13 Raman scattering spectroscopy is a nondestructive tool for the qualitative and quantitative analysis of residual deformations in nitride epilayers.…”

Growth of AlInN/GaN distributed Bragg reflectors with improved interface quality

“…AlInN/GaN-DBR structures were deposited on optimized GaN buffers consisting of low temperature AlN-seed layers, 200 nm AlN, 100 nm AlGaN compositionally graded transition layers, in-situ SiN mask for reduction of the threading dislocation density and 3.5 mm thick GaN. This buffer structure leads to compressive pre-stress of the GaN and typical dislocation densities in the lower range of 10 8 cm À 2 , as determined by X-ray diffraction analysis [14]. All AlInN films were grown under nitrogen as carrier gas at a temperature of 800 1C, reactor pressure of 70 mbar and nitrogen flow of 900 sccm, while for the GaN growth pressure and ammonia flow were raised to 200 mbar and 2000 sccm, respectively.…”

Форма Распределения Интенсивности Рентгеновской Дифракции В Обратном Пространстве И Ее Связь С Дислокационной Структурой Эпитаксиальных Слоев

“…Такая дислокационная струк-тура характерна для эпитаксиальных слоев III-нитридов (GaN, AlN, InN), для которых при больших рассогласованиях параметров решет-ки с подложкой затруднено образование параллельных интерфейсу дислокаций. Распределение интенсивности в этом случае вытянуто параллельно поверхности как для симметричных, так и асимметричных рефлексов [3][4][5][6][7]. Конечно, мы не должны отбрасывать размерный эффект.…”