Three-dimensional reciprocal space mapping of diffuse scattering for the study of stacking faults in semipolar (\bf 11{\overline 2}2) GaN layers grown from the sidewall of anr-patterned sapphire substrate

Abstract

Three-dimensional reciprocal space mapping of semipolar (11{\overline 2}2) GaN grown on stripe-patternedr-plane (1{\overline 1}02) sapphire substrates is found to be a powerful and crucial method for the analysis of diffuse scattering originating from stacking faults that are diffracting in a noncoplanar geometry. Additionally, by measuring three-dimensional reciprocal space maps (3D-RSMs) of several reflections, the transmission electron microscopy visibility criteria could be confirmed. Furthermore, similar to cathodoluminescence, the 3D-RSM method could be used in future as a reliable tool to distinguish clearly between the diffuse scattering signals coming from prismatic and from basal plane stacking faults and from partial dislocations in semipolar (11{\overline 2}2) GaN. The fitting of the diffuse scattering intensity profile along the stacking fault streaks with a simulation based on the Monte Carlo approach has delivered an accurate determination of the basal plane stacking fault density. A reduction of the stacking fault density due to the intercalation of an SiN interlayer in the GaN layer deposited on the sidewall of the pre-patterned sapphire substrate has led to an improvement of the optoelectronic properties, influenced by the crystal quality, as has been demonstrated by a locally resolved cathodoluminescence investigation.

Semipolar (202¯1) GaN and InGaN quantum wells on sapphire substrates

“…8 The high relative intensity of NBE to BSF related emission (NBE to BSF intensity ratio of 2.8), and the narrow linewidth of the GaN bandedge emission of 14 meV indicate high microstructural quality, especially when compared to semipolar or nonpolar GaN on planar sapphire substrates. 8,9,26 Further, techniques such crystal shaping for defect bending and blocking 16,27 and use of in-situ grown interlayers 28,29 have shown additional improvement in microstructural quality with growth on patterned sapphire is possible.…”

Three-dimensional reciprocal space mapping with a two-dimensional detector as a low-latency tool for investigating the influence of growth parameters on defects in semipolar GaN

“…(5) Quantification of the BSF density using Monte Carlo simulations of the streak profile was established and described in detail in previous work by Barchuk et al (2011), who have developed the underlying model based on a Monte Carlo simulation approach which determines the BSF densities from the diffuse scattering along the streak for semipolar (1122) GaN (Lazarev et al, 2013). In our previous work, the PL measurements of the semipolar (1122) GaN provided evidence of a strong defect-correlated luminescence at 3.43 eV attributed to BSFs of type I 1 (Lazarev et al, 2013;Scholz et al, 2014;Schwaiger et al, 2010). Furthermore, the luminescence peak appearing at 3.32 eV, assigned to BSFs of type I 2 , is significantly weaker than the band of 3.43 eV originating from BSFs of type I 1 for the two surface orientations studied, 1011and 1122 (Scholz et al, 2014).…”

“…Such structures typically suffer from huge densities of stacking faults (Scholz et al, 2014, and references therein), so the analysis and optimization of such structures with respect to these defects is strongly required. Typically, the basal plane stacking fault (BSF) density in nonpolar structures is larger than 10 5 cm À1 (Moram, Johnston, Hollander, Kappers & Humphreys, 2009;Barchuk et al, 2011), while semipolar GaN grown on prepatterned sapphire substrates has revealed a BSF density at least two orders of magnitude lower (Scholz et al, 2014;Lazarev et al, 2013). Romanov et al (2006) have calculated the total polarization discontinuity for In x Ga 1Àx N layers coherently strained to GaN for crystallographic orientations varying between polar c plane ( = 0 ) and nonpolar ( = 90 ) for different indium contents.…”

“…Three-dimensional reciprocal-space mapping of X-ray diffuse scattering has recently been demonstrated by Lazarev et al (2013) to be a reliable method for accurately determining the stacking fault densities of semipolar (1122) GaN grown on an r-plane (1123) PSS, where the X-ray diffuse scattering originates from stacking faults which are diffracting in noncoplanar geometry. The stacking fault densities were determined quantitatively using Monte Carlo simulations of the diffuse scattering profile along the streak derived from threedimensional reciprocal-space maps (3D-RSMs).…”

“…The stacking fault densities were determined quantitatively using Monte Carlo simulations of the diffuse scattering profile along the streak derived from threedimensional reciprocal-space maps (3D-RSMs). However, the acquisition of 3D-RSMs performed by Lazarev et al (2013) using a linear detector (Mythen 1K) was a time-consuming experiment which took typically up to 12 h. This procedure appears to be inconvenient for planned in situ metal-organic vapour phase epitaxial (MOVPE) experiments which are currently in preparation, aimed at following the evolution of defects during growth. For that reason, the development of a rapid nondestructive defect assessment and quantification method such as three-dimensional reciprocal-space mapping using a fast read-out two-dimensional detector with a high dynamic range, suited to in situ synchrotron investigation of the growth process, is crucially required to provide fast feedback to crystal growers and to support the development of reduced defect density GaN.…”