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Kouvetakis J, Wallace PM, Xu C, Ringwala DA, Mircovich M, Roldan MA, Webster PT, Grant PC, Menéndez J. Synthesis of High Sn Content Ge 1-x-ySi xSn y (0.1 < y < 0.22) Semiconductors on Si for MWIR Direct Band Gap Applications. ACS APPLIED MATERIALS & INTERFACES 2023; 15:48382-48394. [PMID: 37801731 DOI: 10.1021/acsami.3c10230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/08/2023]
Abstract
A systematic effort has been described to grow ternary Ge1-x-ySixSny semiconductors on silicon with high Sn concentrations spanning the 9.5-21.2% range. The ultimate goal is not only to produce direct band gap materials well into the infrared region of the spectrum but also to approach a critical concentration (yc) for which further additions of Si would decrease─rather than increase─the band gap. This counterintuitive behavior is expected as a result of the giant bowing parameter in the compositional dependence of the band gap associated with the presence of Si-Sn pairs. The growth approach in this study was based on a chemical vacuum deposition method that uses Si4H10, Ge3H8, and SnD4 or SnH4 as the sources of Si, Ge, and Sn, respectively. A fixed Si concentration near x = 0.05-0.07 was chosen to focus the exploration of the compositional space. A first family of samples was grown of Ge-buffered Si substrates. For Sn concentrations y < 0.12, it was found that the samples relaxed their mismatch strain in situ during growth, resulting in high Sn content films that had relatively low levels of strain and exhibited photoluminescence signals that demonstrated direct band gap behavior for the first time. The device potential of these materials was also demonstrated by fabricating a prototype photodiode with low dark currents. The optical studies suggest that the above-mentioned critical concentration is close to yc = 0.2. As the growth temperature was lowered in an effort to reach such values, Sn concentrations as high as y = 0.15 were obtained, but the films grew fully strained with compressive levels as high as 1.7%. To increase the Sn concentration beyond y = 0.15, a new strategy was adopted, in which the Ge buffer layer was eliminated, and the ternary alloy was grown directly on Si. The much higher lattice mismatch between the Ge1-x-ySixSny layer and the Si substrate caused strain relaxation right at the film/substrate interface, and the subsequent films grew with much lower levels of strain. This made it possible to lower the growth temperatures even further and achieve a comprehensive series of strained relaxed samples with tunable Sn concentrations as high as y = 0.21 (and beyond). The latter represent the highest Sn contents in crystalline Ge1-x-ySixSny attained to date and reach the desired yc = 0.2 range. The synthesized films exhibited significant thickness, allowing a thorough determination of composition, crystallinity, morphology, and bonding properties, indicating the formation of single-phase single-crystal alloys with random cubic structures. Further work will focus on optimizing the latter samples to explore the optical and electronic properties.
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Affiliation(s)
- John Kouvetakis
- School of Molecular Science, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Patrick M Wallace
- School of Molecular Science, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Chi Xu
- Department of Physics, Arizona State University, Tempe, Arizona 85287-1504, United States
| | - Dhruve A Ringwala
- School of Molecular Science, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Matthew Mircovich
- Department of Physics, Arizona State University, Tempe, Arizona 85287-1504, United States
| | - Manuel A Roldan
- Eyring Materials Center Arizona State University, Tempe, Arizona 85287-1504, United States
| | - Preston T Webster
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, New Mexico 87117, United States
| | - Perry C Grant
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, New Mexico 87117, United States
| | - José Menéndez
- Department of Physics, Arizona State University, Tempe, Arizona 85287-1504, United States
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Zhou T, Zhong Z. Optical properties demonstrating strong coupling of compactly arranged Ge quantum dots. OPTICS EXPRESS 2019; 27:22173-22180. [PMID: 31510512 DOI: 10.1364/oe.27.022173] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 07/10/2019] [Indexed: 06/10/2023]
Abstract
Coupled quantum dots (QDs) have been extensively investigated for their unique collective properties and potential applications in optoelectronic devices. Herein, dense Ge QDs with a compact arrangement in-plane are readily obtained. Systematic studies on power-dependent photoluminescence (PL) from the QD ensemble demonstrate a PL peak with a superior intensity, a constant peak energy and width as a function of the excitation power. Moreover, the temperature-dependent PL spectra exhibit a pronounced red-shift and a rapid PL quenching with increasing temperature. Such PL properties are attributed to the formation of miniband and the delocalization of holes in the QD ensemble due to the strong coupling between closely adjacent QDs.
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Wang Z, Wang S, Yin Y, Liu T, Lin D, Li DH, Yang X, Jiang Z, Zhong Z. Promising features of low-temperature grown Ge nanostructures on Si(001) substrates. NANOTECHNOLOGY 2017; 28:115701. [PMID: 28140355 DOI: 10.1088/1361-6528/aa5b3d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
High-quality Ge nanostructures are obtained by molecular beam epitaxy of Ge on Si(001) substrates at 200 °C and ex situ annealing at 400 °C. Their structural properties are comprehensively characterized by atomic force microscopy, transmission electron microscopy and Raman spectroscopy. It is disclosed that they are almost defect free except for some defects at the Ge/Si interface and in the subsequent Si capping layer. The misfit strain in the nanostructure is substantially relaxed. Dramatically strong photoluminescence (PL) from the Ge nanostructures is observed. Detailed analyses on the power- and temperature-dependent PL spectra, together with a self-consistent calculation, indicate the confinement and the high quantum efficiency of excitons within the Ge nanostructures. Our results demonstrate that the Ge nanostructures obtained via the present feasible route may have great potential in optoelectronic devices for monolithic optical-electronic integration circuits.
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Affiliation(s)
- Ze Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, People's Republic of China. Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
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Temperature dependence of the direct gaps of ZnSe and Zn0.56Cd0.44Se. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:1819-1824. [PMID: 9986029 DOI: 10.1103/physrevb.54.1819] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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