Electronic Signature of Subnanometer Interfacial Broadening in Heterostructures

Abstract

Interfaces are ubiquitous in semiconductor low-dimensional systems used in electronics, photonics, and quantum computing. Understanding their atomic-level properties has thus been crucial to controlling the basic behavior of heterostructures and optimizing the device performance. Herein, we demonstrate that subnanometer interfacial broadening in heterostructures induces localized energy states. This phenomenon is predicted within a theory incorporating atomic-level interfacial details obtained by atom probe tomography. The experimental validation is achieved using heteroepitaxial (Si1–x Ge x ) m /(Si) m superlattices as a model system demonstrating the existence of additional paths for hole–electron recombination. These predicted interfacial electronic transitions and the associated absorptive effects are evaluated at variable superlattice thickness and periodicity. By mapping the energy of the critical points, the optical transitions are identified between 2 and 2.5 eV, thus extending the optical absorption to lower energies. This phenomenon is shown to provide an optical fingerprint for a straightforward and nondestructive probe of the subnanometer broadening in heterostructures.

Three-Dimensional Reconstruction of Interface Roughness and Alloy Disorder in Ge/GeSi Asymmetric Coupled Quantum Wells Using Electron Tomography

“…As a matter of fact, breaking the in-plane invariance, the roughness acts as a perturbing potential that can be fully characterized in terms of the above-mentioned structural parameters, largely impacting, for instance, the lifetime of the laser transition . To determine the actual 3D morphology of Ge/GeSi interfaces in coupled QW systems with high spatial resolution, atom probe tomography (APT) has been recently employed. − …”