Theory and design of quantum cascade lasers in (111) n-type Si/SiGe

TL;DR

This paper proposes a new design approach for quantum cascade lasers in (111) n-type Si/SiGe heterostructures, overcoming previous limitations and predicting feasible operation at temperatures up to 90 K.

Contribution

It demonstrates that (111) growth direction in Si/SiGe heterostructures enhances band offset and preserves degeneracy, enabling practical quantum cascade laser designs in silicon-based materials.

Findings

Net gain predicted up to 90 K temperature.

Large band offset and low effective mass achievable.

Interdiffusion length of 8 Å tolerated.

Abstract

Although most work toward the realization of group IV quantum cascade lasers (QCLs) has focused on valence-band transitions, there are many desirable properties associated with the conduction band. We show that the commonly cited shortcomings of n-type Si/SiGe heterostructures can be overcome by moving to the (111) growth direction. Specifically, a large band offset and low effective mass are achievable and subband degeneracy is preserved. We predict net gain up to lattice temperatures of 90 K in a bound-to-continuum QCL with a double-metal waveguide, and show that a Ge interdiffusion length of at least 8 angstroms across interfaces is tolerable.