Anisotropic strain relaxation of GaInP epitaxial layers in compression and tension

Abstract

Structural and optical properties of strainrelaxed InAsP/InP heterostructures grown by metalorganic vapor phase epitaxy on InP(001) using tertiarybutylarsine We have investigated the strain relaxation of intentionally lattice mismatched (Ϯ0.5%͒ GaInP layers grown on GaAs substrates by organometallic vapor phase epitaxy. Double axis x-ray diffraction was used to measure the relaxation in these epitaxial layers in perpendicular ͗110͘ directions as a function of thickness. For samples in tension, the difference in relaxation between ͓110͔ and ͓110͔ increases from 10% to 48% as the layer thickness increases from 7 to 28 times the critical thickness, h c . For samples in compression this difference is 28% at 24h c while no relaxation is measured for a sample at 6h c . These results indicate that strain relaxes anisotropically and that the anisotropy is more pronounced for samples in tension than in compression. Furthermore, the major relaxation axis was found to be ͓110͔ regardless of the sign of the strain. Reciprocal space maps, generated using triple axis x-ray diffraction, showed that the amount of microtilt of the epitaxial layers was also anisotropic. This anisotropy and the direction of the maximum dislocation density which was measured by cathodoluminescence and transmission electron microscopy, changed from ͓110͔ in tension to ͓110͔ in compression. The fact that the major relaxation axis remained stationary while the high misfit dislocation density direction rotated indicates that a substantial number of dislocations with Burgers vectors of the ''wrong sense'' for strain relief are formed in compressed epilayers. A model in which ␣ type dislocations are more mobile than the ␤ type misfit dislocations regardless of the sign of the strain is consistent with all of the experimental observations.

Role of InAs and GaAs terminated heterointerfaces at source/channel on the mixed As-Sb staggered gap tunnel field effect transistor structures grown by molecular beam epitaxy

“…It is well established that the formation kinetics of these two types of dislocations are different, which leads to observed asymmetric strain relaxation along both h110i directions. 39 However, from our study on these TFET structures, the strain relaxation value extracted along [1 10] 38 buffer materials. The symmetric relaxation in these layers indicates that the total length of misfit dislocation in each h110i direction is approximately the same.…”

“…In compressively strained III-V layer, an a type dislocation lies in the [1 10] direction. 39 Similarly, a b type dislocation lies in the [110] direction to relieve compressive strain in the epilayer. 39 As a result, for strain relaxation by misfit component of 60 dislocations, relaxation along the [1 10] direction is controlled by the nucleation and glide of b dislocations and relaxation along the [110] direction is controlled by the nucleation and glide of a dislocations, respectively.…”

“…39 Similarly, a b type dislocation lies in the [110] direction to relieve compressive strain in the epilayer. 39 As a result, for strain relaxation by misfit component of 60 dislocations, relaxation along the [1 10] direction is controlled by the nucleation and glide of b dislocations and relaxation along the [110] direction is controlled by the nucleation and glide of a dislocations, respectively. It is well established that the formation kinetics of these two types of dislocations are different, which leads to observed asymmetric strain relaxation along both h110i directions.…”

Synchrotron topography and X-ray diffraction study of GaInP layers grown on GaAs/Ge

“…Remarkably, the MDs are completely absent in the ½1 1 0 direction. Asymmetric strain relaxation in dense MD networks is a known phenomenon [19] and has been observed in Ga 1Àx In x P grown on GaAs substrates [16]. However, the density of the MDs in sample B is found to be so small that the strain in the sample is only nominally relaxed, as evidenced by the RSM of Figs.…”

“…The strain is tensile in both epilayers of sample B, but the Ga 0:5094 In 0:4906 P layer is less strained than the GaAs layer. 224 RSMs measured from Ga 1Àx In x P epilayers having either large tensile strain ðx ¼ 0:41Þ or large compressive strain ðx ¼ 0:55Þ on GaAs substrates are known to show asymmetricity due to the asymmetric strain relaxation of Ga 1Àx In x P on GaAs [16]. Some differences in the shapes of the X-ray maxima arising from the asymmetric strain is observed in RSMs of Figs.…”