Towards Group-IV Spin-Optoelectronics

• Applicant: Dr.-Ing. Markus Lindemann
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 464292692

The growing demand for extremely fast optical data transmission technology requires the development of novel laser concepts with very fast modulation capabilites and a good energy efficiency. Additionally it is very advantageously to design future laser concepts to be compatible with Si-based platforms in order to be directly integrated into electronic circuits, allowing for, e.g., fast on-chip data transmission or transmissions between microprocessor and memory. The applicant was able to demonstrate that spin-lasers offer extremely fast modulation bandwidths above 200 GHz in a recent Nature publication. In spin-lasers, instead of the intensity, the polarization of the laser emission is modulated. Thus, due to the unique properties of the polarization dynamics faster and more energy efficient modulation can be obtained compared to utilizing conventional intensity modulation. The spin-laser was based on a vertical-cavity surface-emitting laser diode in the GaAs material system and thus it is not possible to directly implement it to a Si-based integrated circuit. The host-institution Eindhoven University of Technology (TU/e) recently developed direct bandgap hexagonal polytype SiGe (hex-SiGe) nanowires, which are very promising for demonstrating a Si-compatible laser. Moreover, the host institution demonstrated efficient room-temperature light emission from direct bandgap SiGe alloys, which was also published in Nature. This proposed project lays the basis for developing ultrafast spin-lasers based on hex-SiGe nanowire active material and opens up the research field of Si-compatible spin-optoelectronics. The main working package of this project is the investigation of the spin-lifetime in hex-SiGe nanowires. It is a fundamental prerequisite for application-oriented spin-lasers that the spin-lifetime is in an appropriate range: On the one hand, it needs to be short enough in order to allow fast polarization dynamics. On the other hand, a too short spin-lifetime decreases the amplitude of the spin-effects and is detrimental for spin-injection. The spin-lifetime will be determined for a large temperature range between 4 K and room temperature utilizing photoluminescence (PL) measurements. For PL excitation, circularly polarized pulses will be used and the PL decay will be measured polarization resolved. Utilizing this procedure the spin-lifetime can be calculated. A further working package is to investigate the capability of the hex-SiGe nanowires to act as gain material in lasers: First, conventional lasing operation and second, spin-lasing operation will be pursued under laboratory conditions using optical pumping. With these first steps, the project lays the foundation for future research to exploit all advantages of combining spin-lasers and the hex-SiGe material system.

• DFG Programme: WBP Fellowship
• International Connection: Netherlands
• Host: Professor Dr. Jos Haverkort