M. F. Schouten, M. A. J. van Tilburg, V. T. van Lange, W. H. J. Peeters, R. Farina, M. M. Jansen, M. Vettori, E. P. A. M. Bakkers, J. E. M. Haverkort
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引用次数: 0
摘要
直接带隙 IV 族半导体,如应变 Ge、GeSn 或六方 SiGe,被认为有望在硅上实现光子集成。对于 IV 族半导体激光器来说,了解带边的载流子冷却效率至关重要。从基础角度来看,研究直接带隙第四族半导体Γ谷内的载流子冷却特别有趣,因为由于非极性晶格的存在,弗洛里希相互作用在这些材料中预计非常微弱,甚至不存在。非极性半导体Γ谷内的谷内载流子弛豫以前从未在实验中获得过,因为它总是被能量接近的间接导带极小值之间的间隔过程所掩盖。在这里,我们研究了直接带隙六方硅锗(hex-SiGe)纳米线中的载流子冷却,从而研究了与间接极小带充分分离的孤立Γ谷中的载流子冷却。我们在六硅锗Γ谷中获得了 180 ps 的热载流子冷却时间。虽然由于不存在弗洛里希相互作用,冷却时间比在块状极性 III/V 族材料中要慢得多,但它与 InGaAs MQW 激光结构中的冷却时间相当。我们的结论是,载流子冷却并不会从本质上限制六硅锗作为激光增益材料。这一结果是对第四族半导体激光器领域的一个重要启示。
Carrier cooling in direct bandgap hexagonal silicon-germanium nanowires
Direct bandgap group IV semiconductors, like strained Ge, GeSn, or hexagonal SiGe, are considered promising for photonic integration on silicon. For group IV semiconductor lasers, it is crucial to understand the carrier cooling efficiency toward the band edges. From a fundamental perspective, a study of carrier cooling within the Γ-valley of direct bandgap group IV semiconductors is particularly interesting since the Fröhlich interaction is expected to be very weak or even absent in these materials due to the nonpolar lattice. Intravalley carrier relaxation within the Γ-valley of a nonpolar semiconductor has not been experimentally accessible before since it has always been overshadowed by intervalley processes between energetically close indirect conduction band minima. Here, we study carrier cooling in direct bandgap hexagonal silicon-germanium (hex-SiGe) nanowires, allowing us to study carrier cooling in an isolated Γ-valley that is sufficiently separated from the indirect minima. We obtain a hot carrier cooling time of 180 ps in the Γ-valley of hex-SiGe. Although the cooling is much slower than in bulk polar group III/V materials due to the absence of Fröhlich interaction, it is comparable to the cooling time in an InGaAs MQW laser structure. We conclude that carrier cooling does not inherently limit hex-SiGe to serve as a laser gain material. This result is an important insight into the field of group IV semiconductor lasers.
期刊介绍:
Applied Physics Letters (APL) features concise, up-to-date reports on significant new findings in applied physics. Emphasizing rapid dissemination of key data and new physical insights, APL offers prompt publication of new experimental and theoretical papers reporting applications of physics phenomena to all branches of science, engineering, and modern technology.
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