| AVS 61st International Symposium & Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM1-ThA |
| Session: | Materials for Quantum Computation |
| Presenter: | Daniel Kaiser, University of Pennsylvania |
| Authors: | D. Kaiser, University of Pennsylvania S. Ghosh, University of New Mexico S.M. Han, University of New Mexico T.R. Sinno, University of Pennsylvania |
| Correspondent: | Click to Email |
In this talk we present a multi-element computational approach for quantitatively describing atomic interdiffusion within a random-alloy SiGe wafer subject to a patterned stress field imposed by an indenter array applied to its surface. The model, and the associated parametric investigations we carry out, are motivated by a recently-proposed approach for forming ordered arrays of heteroepitaxial Ge quantum dots (QD) on semiconductor substrates in a scalable and robust manner. In this approach, patterned compositional redistribution of Si and Ge atoms is driven by an applied stress field under thermal annealing. The resulting compositional heterogeneity is shown to induce an internal stress field in the SiGe substrate wafer that persists after the indenter array is removed, thereby effectively “transferring” the stress pattern of the indenter into the substrate. The transferred stress pattern, which we study in detail as a function of several parameters including indenter geometry and thermal annealing schedule, is then used to drive patterning in a subsequent Ge deposition step.
The interdiffusion model is based on a combination of lattice kinetic Monte Carlo (LKMC) and static energy minimization. The LKMC simulation is propagated using rates for atomic diffusion that depend explicitly on local values of stress, composition, and temperature. The dependence of atomic diffusion on composition is regressed to experimental data while the stress dependence is described using the theory of activation volumes [1]. The stress field is updated quasi-statically using a separate energy minimization routine with forces computed based on a Tersoff interatomic potential for the Si-Ge system [2]. The atomic stresses and identities are then smoothed to generate continuous fields that are used as input into the LKMC simulation.
Using our model, we establish that atomic redistribution is feasible for reasonable indenter forces and annealing times and temperatures. We compute the corresponding internal stresses in the compositionally patterned film for several different annealing conditions and show that these stresses are likely to be large enough to influence subsequent Ge quantum dot nucleation and growth. We also compare our results to recent experimental measurements.
References:
[1] M. J. Aziz, Applied Physics Letters 70, 2810 (1997).
[2] J. Tersoff, Physical Review B 39, 5566 (1989).