Review of Si-Based GeSn CVD Growth and Optoelectronic Applications (original) (raw)
Related papers
Investigation of Critical Technologies of Chemical Vapor Deposition for Advanced (Si)GeSn Materials
Masters Thesis, 2019
The development of new materials for efficient optoelectronic devices from Group IV elements is the heart of Group IV photonics. This has direct ties to modern technology as the foundation for the electronics industry is silicon. This has driven the development of siliconbased optoelectronics using these other Group IV materials as silicon is a poor optical material due to its indirect band gap when compared to the III-V semiconductors that are used by most of the optoelectronics industry. While efforts have been made to integrate III-V materials onto silicon substrates, the incompatibility with the complementary metal oxide semiconductor process has limited the viability of this due to the high cost associated with the integration. Germanium has shown potential to be a suitable candidate for possible use though the wavelength range that can be covered is limited as it produces direct bandgaps under tensile strain. Tin-based group IV alloys have been studied and have promising potential in achieving high efficiency optoelectronic devices integrated on silicon. Alloys of germanium-tin have produced many direct bandgap optical devices that have demonstrated the potential for this system. Silicon-germanium-tin alloys hold promise for further expansion of group IV photonics by allowing bandgap and lattice tunability for more complicated device structures and material integrations. The work presented in this thesis was focused on the critical technologies used to develop these materials using ultra-high vacuum chemical vapor deposition for the epitaxial deposition of films with high optical material qualities. Germanium films were grown at low temperature as well as germanium-tin alloys with highly diluted gas ratios directly on silicon substrates. The germanium films served as buffer layers onto which high quality germanium-tin was deposited using silicon substrates. The growth conditions for the geranium-tin alloys began with a high flow fraction of tin (IV) chloride. The flow fraction of tin (IV) chloride was reduced which led to an improvement in material quality. By using x-ray diffraction, photoluminescence, and other characterization tools material and optical qualities could be determined. This work additionally looked at the initial phase of development of silicon-germanium towards a rhombohedral crystal phase using sapphire substrates. Acknowledgement I would to thank advisor, Dr. Shui-Qing (Fisher) Yu, for his unending support in completion of this thesis. His encouragement during this phase of my career have helped me improve in many areas and his leadership has helped me understand the importance of the research and the potential that I have as a researcher. In my journey to reach this point I could think of no other supervisor or advisor that could have seen me through to this end as he has done. I would like to thank Dr. Hameed Naseem for his insight and discussions with things that I did not quite understand about the Custom built CVD system and its needs. I would like to thank Dr. Salamo for agreeing to be on my thesis committee. I would like to thank Dr. Aboozar Mosleh for introducing me to the world of chemical vapor deposition and helping me understand the systems operation and teaching the techniques needed to grow the materials used for this research. I would like to thank Dr. Seyed Amir Ghetmiri for teaching me how to operate and take care of the optical characterization tools that were necessary for this research. I would like to thank Dr. Rick Wise for his understanding and gentle reminders that I needed at times. I would like to thank Mr. Ken Vickers who brought me into the microelectronics-photonics program during a summer research experience for undergraduates and showing me a more interesting career path than the one I had started with. I would like to thank the Institute for Nanoscience and Engineering for use of the characterization tools. I would also like to thank Dr. Andrian Kuchuk for assisting me in measurements and sample preparation. I would like to finally like to thank all of the members of the research group that helped with various measurements and calculations, and shared information from their own work to help improve the teams efforts. I would like to thank the growth team members who showed me the way and encouraged me to keep improving everyday. Without the growth team members working together, the pace at which the research progressed would have been substantially reduced.
UHV-CVD Growth of High Quality GeSn Using SnCl4: From Growth Optimization to Prototype Devices
arXiv (Cornell University), 2018
The persistent interest of the epitaxy of group IV alloy GeSn is mainly driven by the demand of efficient light source that could be monolithically integrated on Si for mid-infrared Si photonics. For chemical vapor deposition of GeSn, the exploration of parameter window is difficult from the beginning due to its non-equilibrium growth condition. In this work, we demonstrated the effective pathway to achieve the high quality GeSn with high Sn incorporation. The GeSn films were grown on Ge-buffered Si via ultra-high vacuum chemical vapor deposition using GeH4 and SnCl4 as precursor gasses. The influence of both SnCl4 flow fraction and growth temperature on the Sn incorporation and material quality were investigated. The key to achieve effective Sn incorporation and high material quality is to explore the proper parameter match between SnCl4 supply and growth temperature, which is also called optimized growth regime. The Sn precipitation is significantly suppressed in optimized growth regime, leading to more Sn incorporation into Ge and enhanced material quality. The prototype GeSn photoconductors were fabricated with typical samples, showing the promising devices applications towards mid-infrared optoelectronics.
CVD Epitaxial Growth of GeSn Opens a New Route for Advanced Sn-Based Logic and Photonics Devices
2012
Interest in Sn-based semiconductors largely increased during the last decade (Fig. 1). If doubts remained in the early 2000's on the hypothetical use of (Si)GeSn epitaxial layers in advanced technologies (mainly due to the low Sn solubility in Si and Ge and the associated reduced thermal stability of those alloys), recent publications from various groups provide today a much better feeling on the potential of those materials. First of all, the growth of GeSn layers with high Sn content was demonstrated by different techniques overruling their apparent thermodynamics limitations. Next, and especially very recently, Sn-based devices are showing up: GeSn MOSCAP, GeSn pMOSFET or GeSn photodetectors for instance. This paper reviews the deposition techniques and different integration schemes to implement GeSn in various technologies and highlights the potential benefits in logic and photonics devices.
Band gap renormalization in n-type GeSn alloys made by ion implantation and flash lamp annealing
Journal of Applied Physics, 2019
The last missing piece of the puzzle for the full functionalization of group IV optoelectronic devices is a direct bandgap semiconductor made by CMOS compatible technology. Here, we report on the fabrication of GeSn alloys with Sn concentrations up to 4.5% using ion implantation followed by millisecond-range explosive solid phase epitaxy. The n-type single crystalline GeSn alloys are realized by co-implantation of Sn and P into Ge. Both the activation of P and the formation of GeSn are performed during a single-step flash lamp annealing for 3 ms. The bandgap engineering in GeSn as a function of the doping level and Sn concentration is theoretically predicted by density functional theory and experimentally verified using ellipsometric spectroscopy. We demonstrate that both the diffusion and the segregation of Sn and P atoms in Ge are fully suppressed by millisecond-range nonequilibrium thermal processing.
Frontiers in Materials, 2015
Germanium-tin alloys were grown directly on Si substrate at low temperatures using a coldwall ultra-high vacuum chemical-vapor-deposition system. Epitaxial growth was achieved by adopting commercial gas precursors of germane and stannic chloride without any carrier gases. The X-ray diffraction analysis showed the incorporation of Sn and that the Ge 1−x Sn x films are fully epitaxial and strain relaxed. Tin incorporation in the Ge matrix was found to vary from 1 to 7%. The scanning electron microscopy images and energy-dispersive X-ray spectra maps show uniform Sn incorporation and continuous film growth. Investigation of deposition parameters shows that at high flow rates of stannic chloride the films were etched due to the production of HCl. The photoluminescence study shows the reduction of band-gap from 0.8 to 0.55 eV as a result of Sn incorporation.
Journal of Electronic Materials, 2020
The binary alloy germanium tin has already been presented as a direct group IV semiconductor at high tin concentrations and specific strain. Therefore, it offers a promising approach for the monolithic integrated light source towards the optical on-chip communication on silicon. However, the main challenge faced by many researchers is the achievement of high tin concentrations and good crystal quality. The key issues are the lattice mismatch to silicon and germanium, as well as the limited solid solubility of tin in germanium of less than 1%. Therefore, this paper presents a systematic investigation of the epitaxial growth conditions of germanium tin with tin concentrations up to 17%. For this, we performed two growth experiments utilizing molecular beam epitaxy. In one experiment, we varied the growth temperature for the epitaxy of germanium tin with 8% tin to investigate the inter-growth temperature stability. In the second experiment, we focused on the strain-relaxation of germanium tin, depending on different tin concentrations and doping types. The results of subsequent material analysis with x-ray diffraction and scanning electron microscopy allow us to narrow the epitaxial window of germanium tin. Furthermore, we present a possible explanation for the unique relaxation mechanism of germanium tin, which is significantly different from the well-known relaxation mechanism of silicon germanium.