X-ray reciprocal-space mapping of strain relaxation and tilting in linearly graded InAlAs buffers

Abstract

The extent of relaxation and orientation of linearly graded InxAl1-xAs (x=0.05–0.25) buffers grown on GaAs were examined using a novel x-ray diffraction reciprocal-space mapping technique (kmap). Samples were grown at temperatures ranging from 370 to 550 °C. The fractional relaxation of the buffers grown between 470 and 550 °C was essentially identical (77%) and symmetric in orthogonal 〈110〉 directions. These buffers are believed to be in equilibrium indicating that the incomplete relaxation is not a kinetic effect. The extent of relaxation was less than that expected for equilibrium relaxation in the absence of dislocation–dislocation interactions indicating that such interactions must be considered to accurately predict the extent of relaxation. The saturation of the relaxation as a function of temperature indicates that at the grading rate used (8% In/μm or 0.69% strain/μm), we are not working in a growth regime where the relaxation is nucleation limited. In addition, all the buffers are slightly tilted with respect to the GaAs substrate about [11̄0] toward the [110] direction suggesting either a bias in the dislocation types in the boule-grown GaAs, or a bias in the way in which α and β dislocations interact with unintentional substrate miscuts.

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

“…The strain relaxation value obtained from our measurement of the uppermost In 0.7 Al 0.3 As layer is consistent with the results obtained by other researchers on the uppermost layer of linear graded In x Al 1-x As buffer. 30,38 There are two types of dislocations exist in III-V compound semiconductors during strain relaxation process. Those related to group-III atoms at their core and belonging to the shuffle set are known as a dislocation, while those shuffle set dislocations with group-V atoms at their core are known as b type.…”

“…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.…”

Triple-axis X-ray Reciprocal Space Mapping of In(y)Ga(1-y)As Thermophotovoltaic Diodes Grown on (100) InP Substrates

“…Reciprocal lattice point (RELP) coordinates are derived from the Ewald sphere construction and diffractometer angular positions ω and 2Θ [4,5] respectively. The RSMs from LM samples were constructed from approximately three-hundred triple-axis ω-2Θ scans (5 asec steps) for ω-offsets spaced 3 asec apart around the (400) and (533) InP substrate RELPs.…”

“…1b provide reciprocal lattice vector components related directly to both the in-plane and out-ofplane lattice parameters. The large Bragg angles and high (hkl) Miller indices of the (533) planes enable greater sensitivity to strain than the more commonly investigated (400, 224, and/or 115) crystal planes [4][5][6][7]. Because of the higher Miller indices, the measured RSM shown in Fig.…”

“…High-resolution x-ray diffraction (HRXRD) reciprocal space mapping (RSM) directly measures the in-plane and out-of-plane lattice parameters, strain, and the diffuse x-ray scattering from multilayered semiconductor heterostructures [3][4]. The technique was recently used to characterize strain-relaxation in linear and step-graded InP 1-x As x and In 1-z Al z As buffers grown by molecular beam epitaxy (MBE) [5][6][7].…”