Innovation of Germanium-tin Alloys in Mid-infrared Spectra 

The rapid development of electronic technology limits its further development and the photonic devices come to being. Ge-based detector has been successfully applied in photonic integration, optical communication and other fields, which promotes the development of semiconductor material and device technology. By incorporating Sn, GeSn-based device can extend the cutoff wavelength into mid infrared wavelength range of 2.0~5.0 μm. It is acknowledged that mid-infrared applications have potential development in free space communication, radar, optical coherence tomography, sensor technology, etc. However, the current research can’t catch up with the requirements for development of GeSn device in mid-infrared (MIR) wavelength.
    The team of Prof. Yue Hao, who is an academician of the Chinese Academy of Sciences, and Prof. Genquan Han from Xidian University, has long been committed to germanium tin material and device. They have done a lot of innovative work in high performance GeSn-based CMOS, Beyond CMOS and GeSn photonic devices in middle infrared domain through theory and experiment. The performance of photonic devices based on GeSn can be improved by adjusting its band structure. By incorporating Sn into Ge, GeSn becomes a direct bandgap material and the strain is introduced to achieve the indirect-to-direct transition without increasing the requirement for Sn composition. The strain induced in GeSn material reduces the EG,Г due to the shift of Γ conduction valley down and HH band up, which is conducive to red shift of absorption edge. The cut-off wavelength of the proposed pillar detector can be extended to 4.35 μm. In the laser applications, a biaxial tensile strain is introduced into the GeSn/SiGeSn MQW laser by the Si3N4 liner stressor. The increase of electron occupation probability in Γ conduction valley is conducive to the improvement of optical emission performance in lasers, which can be achieved by increasing Sn content. The proposed laser shows a Jth reduction from 476 to 168 A/cm2 and a significant enhancement of optical gain. The proposed strategy will promote the development of optoelectronics application in mid-infrared (MIR) wavelength. 

The Main Team Members
Prof. Yue Hao is an academician of the Chinese Academy of Sciences, a senior member of the IEEE, executive director of the Chinese Association of Electronics, and an academician of the Chinese Academy of Sciences. He leads the experts group for the implementation of the major sci-tech items of “core electronic devices, high-end universal chips and basic software products”. He leads the microelectronic technology experts group of the General Armament Department of the People’s Liberation Army of China. He has published more than 150 papers. 
Dr. Genquan Han is the professor of Xidian University. He has accumulated rich experience and made achievements during the long-term work and research. He has made a number of breakthroughs in high mobility channel CMOS and Beyond CMOS devices, including the implementation of high performance strain germanium-tin, strain germanium and InGaAs MOSFET devices, germanium-tin tunneling field effect transistor and the negative capacitance of the transistor. He has published more than 150 papers, more than 30 patents. He has been an invited speaker in international conferences for 10 times and served as chairman of the international conference.


Fang C Z, Liu Y, Zhang Q F, Han G Q, Gao X et alGermanium-tin alloys: applications for optoelectronics in mid-infrared spectra. Opto-Electronic Advances 1, 180004 (2018).