Lattice engineered compliant substrate for defect-free heteroepitaxial growth

Abstract

Presented here is proof-of-principle that a thin single crystal semiconductor film—when twist-wafer bonded to a bulk single crystal substrate (of the same material)—will comply to the lattice constant of a different single crystal semiconductor thick film grown on its surface. In our experiment, a 100 Å film of GaAs was wafer bonded to a GaAs bulk substrate, with a large twist angle between their 〈110〉 directions. The resultant twist boundary ensures high flexibility in the thin film. Dislocation-free films of In0.35Ga0.65P(∼1% strain) were grown with thicknesses of 3000 Å, thirty times the Matthews–Blakeslee critical thickness, on twist-wafer-bonded films of GaAs.

Mapping strain fields in ultrathin bonded Si wafers by x-ray scattering

“…[2][3][4][5] Such bonded wafers have aroused considerable interest because they open up unique possibilities for device fabrication. 6 Particularly interesting are applications that use them as templates in epitaxial growth 7 or for creating nanometer periodic surface structures by selective etching. 8 X-ray scattering measurements of the strain field in thick bonded wafers with different twist angles twist have been reported previously.…”

Plastic Relaxation Mechanics in Systems with a Twist-Bonded Layer

“…The system displays two interfaces along the [001] axis: i) a heterointerface between the lattice-mismatched layer and the twist-bonded layer and ii) a twist-bonded interface between this twist-bonded layer and the host substrate below. The position of rows of atoms above (below) the twist-bonded interface is denoted by integer numbers nI and n 2 (n 3 and n 4 ) in surface lattice units along the [110] and [1][2][3][4][5][6][7][8][9][10] directions. The twist-bonded layer and the host substrate are rotated one with respect to the other around the [001] axis by 16.26' that corresponds to the grain boundary 12s.…”

“…The way this sticking is done reveals the way the relaxation is presumed to act. If an intermediate viscous layer is used to stick the compliant layer to its host substrate, an elastic relaxation is guessed acting [6,7] whereas any attempt to weaken the interface by for example twisting and/or tilting the compliant axes relative to the host substrate ones means that some kind of plastic relaxation is expected [8][9][10][11][12][13].…”

Compliant substrate technology for dissimilar epitaxy

“…Again, this seems rather unlikely, but cannot yet be discounted. THE CORNELL APPROACH: A second experiment using a different type of substrate raised the excitement levels to even greater heights [5][6][7]. The compliant substrate in this case was essentially just two GaAs wafers bonded together with an in-plane twist misorientation, and then thinned from one side to create a thin single crystal layer joined to a handle wafer by a twist grain boundary (see Figure 2b).…”

“…CnG (Y. H. Lo) pioneered the original concept of the practical compliant substrate [1] and produced the f~st twist-bonded "compliant universal substrates" of GaAs/GaAs and Si/Si [5][6][7]. Initial results suggested major reductions in threading defect densities for strained layer growth on twist-bonded substrates vs. bulk substrates.…”