Research On Si Based Modified Ge Materials Growth And Their Optoelectronic Applications

Si-based monolithic optoelectronic integration technology is committed to using silicon-compatible semiconductor processes to integrate photonic devices on silicon chips,thereby improving chip performance or expanding chip functions and reducing costs.Although silicon-based photonics devices,such as,optical waveguides,photodetectors,optical modulators,and optical switches have been successfully developed,it is difficult to achieve high-efficiency light source due to the indirect band gap characteristics of Si.Therefore,Si-based high-efficiency light source is an important technical bottleneck restricting Si-based monolithic optoelectronic integration.Looking for a direct band-gap semiconductor material that is compatible with traditional Si CMOS technology is of great significance.Ge material,which is also Group IV element,has attracted researchers'wide attention due to its bandgap difference between the direct band gap and indirect band gap is only 136 m V.Moreover,its band gap structure can be adjusted through strain engineering and Sn alloy engineering.Si-based high-efficiency light source,as the core component of Si-based monolithic integrated chips,plays a vital role in achieving high-efficient,high-speed,and low-loss data transmission.This paper focuses on the epitaxial growth of modified Ge materials and key technologies to achieve their coherent light-emitting devices:we prepare the high-quality modified Ge light-emitting materials,and systematically study their material characteristics;design and optimize the fabrication process for the strained Ge materials light-emitting device,continuous-wave electrically injected strained Ge light-emitting diodes is achieved;optical and thermal parameters for microdisk cavity GeSn laser are well designed and optimized,which is expected to work at room temperature.The main research highlights are as follows:1.Research on the growth of Si-based Ge materials using RPCVD.Combined the low temperature-high temperature two-step method with low temperature Si buffer layer,surface roughness,dislocation density,and tensile strain in single crystal Ge layer is 0.68nm,3×10⁶ cm^-2,and 0.21%,respectively.Based on the single crystal Ge recipe,P-type doping,in-situ cyclic annealing,in-situ high-temperature H₂ annealing,and Si cap layer were performed to achieve the high-quality p-Ge/i-Ge/i-Si layer light-emitting device structure with 0.23%tensile strain,which laid a solid foundation for the subsequent design and development of Ge-based light-emitting devices.2.Study on the dislocation density for Si-based Ge materials.Rocking curve method was proposed to calculate the dislocation density in the Ge epitaxial layer.The results show that the dislocation density(1.41×10⁸ cm^-2)obtained by the rocking curve method is one to two orders of magnitude higher than that obtained by the etch pit method and TEM method.The proposed method simplifies the dislocation density characterization process for the Ge epitaxial layer,and also reduces the dislocation density characterization cost for the Ge epitaxial layer.At the same time,it effectively avoids the damage to the Ge epitaxial layer samples that caused by defect characterization,and it also helps to accelerate the research progress for Ge epitaxial materials.3.Research on the growth technology of Si-based GeSn materials based on PVD.The DC magnetron sputtering method was used to realize the growth of GeSn materials with high Sn composition on Si(100)and Si(111)substrates,and the segregation mechanism of GeSn materials with high Sn composition was systematically studied.Afterwards,high-quality GeSn with Sn composition up to 3%was achieved on the Ge buffer layer by radio frequency magnetron sputtering,and photoluminescence signals were observed at room temperature,indicating GeSn prepared by this method can be used for the fabrication of light-emitting devices,and it is also the world record achieving the photoluminescence signal of GeSn alloy prepared by physical vapor deposition method.4.Research on key technologies of strained Ge edge-emitting devices.N-type ion implantation process,the device fabrication process of strained Ge light-emitting diodes,and its packaging process were well designed and optimized.Room temperature Continuous wave electrically injected strained Ge light-emitting diodes were obtained.1640-1645nm.Meanwhile,temperature-dependence electrically injected strain Ge laser measurement setup is carefully designed.This setup can effectively avoid the influence of thermal effect on the performance of the strain Ge laser,which is conducive to the study of the lasing behavior of strained Ge laser.This setup will be the first temperature-dependence laser measurement set for group IV lasers in China.5.Research on the optical and thermal design for GeSn microdisk cavity laser.In order to improve the operation temperature for GeSn microdisk laser,a thermal management strategy based on high thermal conductivity metal material bonding is proposed,which is beneficial for achieving high Sn composition and high performance GeSn microdisk laser.A thin Si layer is induced as a heat transfer medium between GeSn layer and Au layer,it can significantly increase its heat transfer rate and reduce the effect of temperature on the Auger recombination and band gap structure in the gain region.When the optical injected power of the GeSn laser is lower than 25 m W,temperature change in the gain region of the GeSn microdisk laser is less than 10 K,which provides a good foundation to achieve the room temperature GeSn microdisk laser.