Roadmap to an Efficient Germanium-on-Silicon Laser: Strain vs. n-Type Doping

• Main Authors: Birendra Dutt, Devanand S. Sukhdeo, Donguk Nam, Boris M. Vulovic, Ze Yuan, Krishna C. Saraswat
• Format: Article
• Language: English
• Published: IEEE 2012-01-01
• Series: IEEE Photonics Journal
• Subjects: Semiconductor lasers; diode lasers; semiconductor materials; optoelectronic materials; infrared lasers; theory and design
• Online Access: https://ieeexplore.ieee.org/document/6327582/

We provide a theoretical analysis of the relative merits of tensile strain and n-type doping as approaches to realizing an efficient low-power germanium laser. Ultimately, tensile strain offers threshold reductions of over 200x, and significant improvements in slope efficiency compared with the recently demonstrated 0.25% strained electrically pumped germanium laser. In contrast, doping offers fundamentally limited benefits, and too much doping is harmful. Moreover, we predict that tensile strain reduces the optimal doping value and that experimentally demonstrated doping has already reached its fundamental limit. We therefore theoretically show large (>; 1%) tensile strain to be the most viable path to a practical germanium-on-silicon laser.