Characterization of metamorphic InxAl1−xAs∕GaAs buffer layers using reciprocal space mapping

Abstract

The depth profiles of metamorphic In x Al 1−x As ͑0.05Ͻ x Ͻ 1͒ buffer layers grown on GaAs substrates were characterized using the x-ray reciprocal space mapping. Three types of metamorphic samples were investigated and compared: step grade, single-slope linear grade, and dual-slope linear grade. The lattice mismatch, residual strain, crystallographic tilt, tilt azimuth, and the full width at half maximum were obtained from the reciprocal space maps. The tilt angle of linearly graded buffer layers stayed low at low In compositions until InϷ 60%, at which composition the tilt angle increased abruptly. All linear-grade samples had an untilted relaxed structure in the low In region ͑below 60% In͒ and a tilted structure in the upper, high In region ͑above 60% In͒. The average lattice mismatch between the untilted relaxed structure and the tilted structure determines the tilt angle. The tilt angle of the step-graded layers increased at a near-linear rate as the In composition was increased. The tilt azimuth was intermediate between the ͗100͘ and ͗110͘ in-plane directions. The x-ray full width at half maximum generally increased with the In composition, but tended lower toward surface. We suggest a possible design strategy for the linear-grade metamorphic buffer layer based on our result.

Evolution of epilayer tilt in thick In Ga1−As metamorphic buffer layers grown by hydride vapor phase epitaxy

“…The tilt behavior was also controlled by the grading style. In a study on In x Al 1 À x As buffer layers grown on (100) GaAs substrates by MBE, Lee et al [22] found that tilt increased more strongly with composition in step-graded layers when compared with continuously-graded layers, similar to results in the present study. The stronger tilting of the step-graded samples relative to the continuously-graded samples might be due the larger, discrete increases in strain during growth of the structure.…”

Features of the diagnostics of metamorphic InAlAs/InGaAs/InAlAs nanoheterostructures by high-resolution X-ray diffraction in the ω-scanning mode

“…We note that results similar to those shown in Fig. 3a were obtained in [2]. It can also be noted in Fig.…”

“…Diffraction reflection curves measured in the ω-scanning mode (ω is varied, 2θ = 2θ B = const, θ B is the Bragg angle for a particular epitaxial layer) carry information about the layer mosaicity [1]. Maps of X-ray scattering at a sample (in angular coordinates or in reciprocal space) not only combine the advantages of diffraction reflection curves in the modes of θ/2θ-and ω-scanning, but also carry fundamentally new information about a sample's crystal structure, in particular about the misorientation of epitaxial layers with respect to each other [2].…”

X-ray diffraction analysis of step-graded InxGa1−xAs buffer layers grown by molecular beam epitaxy

“…It has been reported that high resolution X-ray diffraction (XRD) is an accurate tool for measuring the strain relaxation through the position of diffraction peaks in reciprocal space mapping (RSM). XRD-RSM is also a good method to investigate the crystallographic quality of epitaxial layers through diffraction peak analysis, such as layer tilting [4][5][6].…”