Study of GeSn (0.524 eV) Single-Junction Thermophotovoltaic Cells Based on Device Transport Model

Based on the transport equation of the semiconductor device model for 0.524 eV GeSn alloy and the experimental parameters of the material, thermal-electricity conversion performance governed by GeSn diode has been systematically studied in its normal and inverted structure. For the normal p+/n (n+/p) structure, it is demonstrated here that an optimal base doping N d(a) = 3 (7)×1018 cm-3 is observed, and the superior p+/n structure can reach the higher performance. To reduce material consumption, an economical active layer can be comprised of 100-300 nm emitter and 3-6 μm base to attain comparable performance as that for the optimal configuration. The results can offer many useful guidelines for the fabrication of economical GeSn thermophotovoltaic devices.

Study on Crystallization Mechanism of GeSn Interlayer for Low Temperature Ge/Si Bonding

Low temperature bonding technologies is necessary in next-generation photonic integrated circuits, such as flexible optoelectronic devices, low dark current Ge/Si devices and so on. Since Germanium-Tin (GeSn) alloy has lower crystallization temperature, in this work, amorphous GeSn with 5% Sn alloy by magnetron sputtering is introduced as an intermediate layer for wafer bonding innovatively. And high strength Ge/Si heterojunction with a crystal GeSn layer is realized without any surface activation process. Two mechanisms in the interlayer crystallization are put forward and substantiated experimentally and theoretically: 1) the a-GeSn turns to be poly-GeSn due to the induction of the c-Ge substrate. 2) Stress between Si wafer and interlayer due to thermal mismatch contributes to the crystallization. It is concluded that GeSn semiconductor interlayer bonding would be one of the potential technologies for bonding process.

Optimization of Laser Recrystallization Process for GeSn Films on Si Substrates Based on Finite Difference Time Domain and Finite Element Method

GeSn alloy on Si substrate has the advantages of high carrier mobility, high radiation recombination efficiency, compatibility with the Si process, and is widely used in the field of semiconductor optoelectronics. However, due to the high lattice mismatch between the GeSn epitaxial layer and the Si substrate, how to prepare a perfect GeSn film on the Si substrate is an issue. The 808 nm continuous wave laser recrystallization technology can significantly improve the quality of the GeSn alloy epitaxial layer by melting and recrystallization, which provide another technical way for solving this problem. Optimized laser recrystallization related process parameters is necessary when laser recrystallization technology is used to prepare high quality GeSn alloy on Si substrate. For this purpose, the absorption, reflection and transmission models of GeSn alloy epitaxial layer/Si substrate system irradiated by 808 nm continuous wave laser are established using finite difference time domain software FDTD Solutions. The thickness-related process parameters of GeSn alloy epitaxial layer and SiO2 capping layer are optimized. In addition, the temperature distribution model of 808 nm continuous wave laser irradiation of GeSn alloy epitaxial layer on Si substrate system is obtained by COMSOL Multiphysics simulation. The process parameters related to laser recrystallization temperature are optimized and listed, which can be used as important technical references for the growth of low defect density GeSn layer on Si substrate assisted by the laser recrystallization technology.