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In this paper we describe state-of-the-art approaches to the modeling of strain relaxation and dislocation dynamics in InGaAs/GaAs (001) heterostructures. Current approaches are all based on the extension of the original Dodson and Tsao plastic flow model to include compositional grading and multilayers, dislocation interactions, and differential thermal expansion. Important recent break-throughs have greatly enhanced the utility of these modeling approaches in four respects: i) pinning interactions are included in graded and multilayered structures, providing a better description of the limiting strain relaxation as well as the dislocation sidewall gettering; ii) a refined model for dislocation-dislocation interactions including zagging enables a more accurate physical description of compositionally-graded layers and step-graded layers; iii) inclusion of back-and-forth weaving of dislocations provides a better description of dislocation dynamics in structures containing strain reversals, such as strained-layer superlattices or overshoot graded layers; and iv) the compositional dependence of the model kinetic parameters has been elucidated for the InGaAs material system, allowing more accurate modeling of heterostructures with wide variations in composition. We will describe these four key advances and illustrate their applications to heterostructures of practical interest.

Modulation-doped Al_0.22Ga_0.78N/GaN heterostructures with various thickness of Si-doped Al_0.22Ga_0.78N barrier (n-AlGaN) were deposited on (0001)-oriented sapphire (α-Al₂O₃) by atmosphere-pressure metal-organic chemical vapor deposition (MOCVD). The reciprocal space mappings (RSMs) of symmetric reflection (0002) and asymmetric reflection were measured by means of the high resolution X-ray diffraction (HRXRD). The results indicate that the microstructures and the strain status of the n-AlGaN barrier correlate to those of the underlying i-GaN layer. The strained n-AlGaN barrier starts to relax when its thickness is 75 nm. It is found that there exists an "abnormal" relaxation state (the strain parameter γ>1) in modulation-doped Al_0.22Ga_0.78N/GaN heterostructures, which maybe results from the internal defects in Al_0.22Ga_0.78N barrier and the strain relaxation status at the i-GaN/α-Al₂O₃ interfaces.

La_0.7Ca_0.3MnO₃(LCMO) thin films with the thickness of 50 nm were deposited on (001)-oriented single crystal SrTiO₃(STO), MgO and α-Al₂O₃(ALO) by 90° off-axis radio frequency magnetron sputtering. Grazing incidence X-ray diffraction technique, associated with normal X-ray diffraction, was performed to measure the in-plane lattice parameter and investigate the lattice strain and strain relaxation in LCMO films. The results indicated that critical thickness of strain relaxation is very small, which may be related to large mismatch between film and substrate. The mechanism for strain relaxation in LCMO film is perhaps different from that for tetragonal distortion.

In this paper we describe state-of-the-art approaches to the modeling of strain relaxation and dislocation dynamics in InGaAs/GaAs (001) heterostructures. Current approaches are all based on the extension of the original Dodson and Tsao plastic flow model to include compositional grading and multilayers, dislocation interactions, and differential thermal expansion. Important recent breakthroughs have greatly enhanced the utility of these modeling approaches in four respects: i) pinning interactions are included in graded and multilayered structures, providing a better description of the limiting strain relaxation as well as the dislocation sidewall gettering; ii) a refined model for dislocation-dislocation interactions including zagging enables a more accurate physical description of compositionally-graded layers and step-graded layers; iii) inclusion of back-and-forth weaving of dislocations provides a better description of dislocation dynamics in structures containing strain reversals, such as strained-layer superlattices or overshoot graded layers; and iv) the compositional dependence of the model kinetic parameters has been elucidated for the InGaAs material system, allowing more accurate modeling of heterostructures with wide variations in composition. We will describe these four key advances and illustrate their applications to heterostructures of practical interest.