转移印刷的多个 Ge$_{0.89}$Sn$_{0.11}$ 薄膜中红外光电探测器
Transfer-printed multiple Ge$_{0.89}$Sn$_{0.11}$ membrane mid-infrared photodetectors
AI总结：
本文制备应变弛豫 Ge$_{0.89}$Sn$_{0.11}$ 薄膜，并通过单次转移印刷制造多个中红外光电探测器，使截止波长延至 $3.1\,μ$m、暗电流降低两个数量级。
摘要：
由于锗锡（Ge$_{1-x}$Sn$_x$）合金具有窄带隙且与硅加工兼容，因此是可扩展集成中红外光子学的多功能平台。这些半导体通常以 Ge 作为中间层生长在硅晶圆上。然而，该异质外延工艺中的巨大晶格失配会导致生长层内积累压应变。这种压应变不仅会使带隙展宽，还限制材料质量及其热稳定性，从而增加覆盖更宽中红外范围所需的 Sn 含量。释放的 Ge$_{1-x}$Sn$_x$ 薄膜为缓解外延应变的这些有害影响并控制带隙能量提供了有效途径，同时还能够实现向不同衬底的混合集成。基于这一视角，本文制备了应变弛豫的 Ge$_{0.89}$Sn$_{0.11}$ 薄膜，随后将其与金属接触一起转移印刷，在单次转移步骤中制造多个光电探测器。所得光电探测器表现出延伸至 $3.1 \,μ$m 波长的光电探测截止波长；与原生生长的光电导器件相比，暗电流显著降低两个数量级。后者由于固有的压应变，其截止波长较短，为 $2.8 \,μ$m。此外，本文还研究了化学处理和退火对器件性能的影响，结果表明暗电流可进一步降低。所展示的转移印刷技术以及粘合层的使用，将允许把多个 GeSn 薄膜转移到几乎任何衬底上。该方法为利用 Ge$_{1-x}$Sn$_x$ 在中波红外范围内可调带隙的混合光电器件的可扩展制造铺平了道路。
英文摘要：
Due to their narrow band gap and compatibility with silicon processing, germanium-tin (Ge$_{1-x}$Sn$_x$) alloys are a versatile platform for scalable integrated mid-infrared photonics. These semiconductors are typically grown on silicon wafers using Ge as an interlayer. However, the large lattice mismatch in this heteroepitaxy protocol leads to the build-up of compressive strain in the grown layers. This compressive strain limits the material quality and its thermal stability besides expanding the band gap, thereby increasing the Sn content needed to cover a broader range in the mid-infrared. Released Ge$_{1-x}$Sn$_x$ membranes provide an effective way to mitigate these harmful effects of the epitaxial strain and control the band gap energy while enabling the hybrid integration onto different substrates. With this perspective, herein strain-relaxed Ge$_{0.89}$Sn$_{0.11}$ membranes are fabricated and subsequently transfer-printed with metal contacts to create multiple photodetectors in a single transfer step. The resulting photodetectors exhibit an extended photodetection cutoff reaching a wavelength of $3.1 \,μ$m, coupled with a significant reduction in the dark current of two orders of magnitude as compared to as-grown photoconductive devices. The latter yields a reduced cutoff of $2.8 \,μ$m due to the inherent compressive strain. Furthermore, the impact of chemical treatment and annealing on the device performance was also investigated showing a further reduction in the dark current. The demonstrated transfer printing, along with the use of an adhesive layer, would allow the transfer of multiple GeSn membranes onto virtually any substrate. This approach paves the way for scalable fabrication of hybrid optoelectronic devices leveraging the tunable band gap of Ge$_{1-x}$Sn$_x$ in the mid-wave infrared range.
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