Ultimate Limit of Biaxial Tensile Strain and N-Type Doping for Realizing an Efficient Low-Threshold Ge Laser

TL;DR

This paper theoretically determines the maximum benefits of biaxial tensile strain and n-type doping in reducing threshold and increasing slope efficiency of Ge-on-Si lasers, identifying ultimate physical limits for optimal design.

Contribution

It quantifies the ultimate limits of biaxial tensile strain and n-type doping for Ge lasers, guiding optimal design parameters for minimal threshold and maximal efficiency.

Findings

Optimal threshold reduction at 3.7% strain and 2x10^18 cm^-3 doping.

Maximum slope efficiency at 2.3% strain and 1x10^19 cm^-3 doping.

Beyond these limits, performance benefits decline.

Abstract

We theoretically investigate how the threshold of a Ge-on-Si laser can be minimized and how the slope efficiency can be maximized in presence of both biaxial tensile strain and n-type doping. Our finding shows that there exist ultimate limits beyond which point no further benefit can be realized through increased tensile strain or n-type doping. Here were quantify these limits, showing that the optimal design for minimizing threshold involves about 3.7% biaxial tensile strain and 2x1018 cm-3 n-type doping, whereas the optimal design for maximum slope efficiency involves about 2.3% biaxial tensile strain with 1x1019 cm-3 n-type doping. Increasing the strain and/or doping beyond these limits will degrade the threshold or slope efficiency, respectively.