Influence of strain on semiconductor thin film epitaxy

Abstract

Under typical growth conditions, strain levels greater than or equal to 10−4 are shown to influence thin film surface morphology and strain relaxation pathways. Misfit and threading dislocations in relaxed heterostructures produce long wavelength undulations on the surface and shallow depressions, respectively. Threading dislocation densities greater than ∼105–106 cm−2 in relaxed heterostructures must be due to increased impediments to dislocation motion, which in turn originate from the effect of the misfit dislocations on the surface morphology. Under typical growth conditions, the origin of strain-induced surface features can be identified by recognizing the length scale at which the features occur.

Strain relaxation mechanism in SiGe-on-insulator fabricated by Ge condensation

“…1. The absence of a cross-hatch pattern, which is commonly observed on the surface of a relaxed or partially relaxed SiGe layer on a bulk Si substrate because of misfit dislocations [15], indicates that the strain in SiGe layer is relaxed without generating dislocations in the oxidation process. The root-mean-square roughness for the 1-h oxidized sample surface is estimated to be 1.5 nm, and that is 1.3 nm for the 2-h one.…”

High-quality metamorphic compositionally graded InGaAs buffers

“…2(b)), which has slight diffraction contrast in the cap indicative of the onset of phase separation, but is otherwise clean and free of any sign of threads, supports this observation. AFM measurements on 40 Â 40 mm and 1 Â 1 mm areas showed the root-mean-squared (RMS) roughness of the wafer surface to be 13.0 nm and 1.6 nm, respectively, with the former value attributable to the growth rate variations that result from strain fields around the misfit dislocations that form along the /0 1 1S directions (the so-called ''cross-hatch'') [21]. This is suitable for most device applications, and chemomechanical polishing (CMP) can be employed if necessary to further smooth the surface.…”

Identification of subsurface damage in freestanding HVPE GaN substrates and its influence on epitaxial growth of GaN epilayers

“…It has been shown that the strain field around dislocations in the SiGe material system can lead to changes in the surface. During epitaxy, this will result in a crosshatch surface morphology representative of the dislocation network [20]. The sample with no evidence of subsurface damage (sample B) was much smoother as seen in Fig.…”