Pseudo single crystal, direct-band-gap Ge0.89Sn0.11 on amorphous dielectric layers towards monolithic 3D photonic integration

Li, Haofeng; Brouillet, Jeremy; Wang, Xiaoxin; Liu, Jifeng

doi:10.1063/1.4902349

Cited by 14 publications

(17 citation statements)

References 24 publications

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“…Furthermore, because of the lower surface energy of Sn compared to Ge, the Sn-rich liquid phase would segregate at the grain boundaries and on the surface of crystallized GeSn. Subsequently, the excess Sn can be easily and selectively etched away using HCl solution, leaving the crystallized GeSn for integrated photonic device fabrication [3,10,21,[26][27][28][29].…”

Section: Substrate-independent Gesn Crystallization On Amorphous Insumentioning

confidence: 99%

“…This phenomenon is in line with the well-defined eutectic temperature in the Ge-Sn equilibrium phase diagram, although the actual crystallization temperature of a-GeSn is beyond the description of the phase diagram due to its nonequilibrium nature. (3) A strong (111) preferred orientation due to minimization of surface energy on amorphous layers [10,21,26,27]. As will be discussed later, this preferred (111) orientation also has a beneficial effect on the strain engineering of GeSn toward direct gap semiconductors.…”

Section: Blanket Gesn Thin Film Crystallizationmentioning

confidence: 99%

“…This observation indicates a slow nucleation rate vs. an extremely fast lateral growth rate during GeSn crystallization induced by the EEC mechanism. Electron backscatter diffraction (EBSD) analyses show that each grain predominantly consists of micro-twins as a result of lateral growth from the same nucleation center upon crystallization [10,26,27]. Figures 2b,c show the crosssectional SEM image and the corresponding energy dispersion X-ray spectroscopy (EDS) mapping for compositional analyses, respectively.…”

Section: Blanket Gesn Thin Film Crystallizationmentioning

confidence: 99%

“…While large grains with high crystallinity are achieved in crystallizing blanket GeSn thin films, the nucleation remains a stochastic process and there is no control of the nucleation site. To pre-define the nucleation sites before crystallization annealing, we have developed three approaches: (1) Sn micropattern induced nucleation [32]; (2) laser seeded nucleation [26][27][28]; and (3) nanotip induced nucleation [26,27].…”

Section: Controlling the Nucleation Location Upon Gesn Thin Film Crysmentioning

confidence: 99%

“…An example of laser-seeded crystallization of Ge 0.89 Sn 0.11 is shown in Figures 5a,b [27]. A laser beam at λ = 514 nm is scanned at one end of a 2 × 38 µm rectangular a-GeSn strip to seed the nucleation of GeSn before furnace annealing.…”

Section: Controlling the Nucleation Location Upon Gesn Thin Film Crysmentioning

confidence: 99%

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GeSn on Insulators (GeSnOI) Toward Mid-infrared Integrated Photonics

Wang

Covian

et al. 2019

Front. Phys.

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In recent years, Ge and Ge 1−x Sn x materials and devices have achieved rapid progress in integrated photonics. However, conventional heteroepitaxy of active photonic devices compromises the area on Si for CMOS electronics, limiting the scale of integration. Furthermore, it is not possible to grow GeSn epitaxially on amorphous and/or flexible substrates toward 3D photonic integration in mid-infrared (MIR) regime. Here, we present low-temperature crystallization of direct bandgap, high crystallinity Ge 1−x Sn x (0.08 < x < 0.26) on amorphous dielectrics insulators (GeSnOI) toward 3D and flexible MIR integrated photonics. Utilizing eutectically-enhanced crystallization (EEC), an extraordinarily large average grain size of ∼100 µm has been achieved in blanket GeSn films crystallized on SiO 2 layers, flexible glass, and polyimide substrates alike. Furthermore, using Sn nanodot enhanced composition enhancement (NICE), we have achieved an average Sn composition as high as 26 at.% to further extend the optical response of GeSn toward λ = 3-5 µm. The achieved Sn composition of 8-26 at.% far exceeds that of the equilibrium solubility limit of <1 at.%, even though the crystallization temperature of 350-450 • C far exceeds the typical epitaxial growth temperature of GeSn. This result indicates that crystallization from amorphous GeSn (a-GeSn) may offer better metastability compared to direct epitaxial growth of GeSn. Attesting to the high crystallinity, a peak optical gain of 2,900 cm −1 with a lifetime approaching 0.1 ns is achieved at λ = 2,200-2,350 nm at 300 K. The gain lifetime is on the same order as epitaxial GeSn, and it is >100x longer than the direct gap transition in Ge, confirming the indirect-to-direct band gap transition in GeSn at ∼9 at. Sn composition. Moreover, a prototype p-GeSn/n-Si photodiode from a-GeSn crystallization achieves 100 mA/W responsivity at λ = 2,050 nm and T = 300 K, approaching the level of some commercial PbS detectors. The device also demonstrates photovoltaic behavior and a low dark current density of 1 mA/cm 2 at −1 V reverse bias, comparable to epitaxial Ge/Si photodiodes. These results indicate that crystallization of GeSnOI offers a promising solution for active devices toward 3D MIR photonic integration and/or MIR photonics on flexible substrates.

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Section: Substrate-independent Gesn Crystallization On Amorphous Insumentioning

confidence: 99%

Section: Blanket Gesn Thin Film Crystallizationmentioning

confidence: 99%

Section: Blanket Gesn Thin Film Crystallizationmentioning

confidence: 99%

Section: Controlling the Nucleation Location Upon Gesn Thin Film Crysmentioning

confidence: 99%

Section: Controlling the Nucleation Location Upon Gesn Thin Film Crysmentioning

confidence: 99%

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GeSn on Insulators (GeSnOI) Toward Mid-infrared Integrated Photonics

Wang

Covian

et al. 2019

Front. Phys.

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Ge‐on‐Si Lasers

Liu¹

2015

Photonics and Electronics With Germanium

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Sn-inserted Al-induced layer exchange for large-grained GeSn thin films on insulator

Toko

Nakata

et al. 2016

Thin Solid Films

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Large-grained polycrystalline GeSn layers on glass are achieved through the layer exchange between aGe and Sn-doped Al layers. The thicker Sn layers, inserted below Al layers, provided the faster growth velocity, resulting in the smaller grain size of the GeSn layer. Controlling the Sn thickness (10 nm) and the growth temperature (300 °C) allowed for approximately 80% (111)-oriented GeSn layer with grains having an average size of 40 μm. The lower growth temperature led to the higher Sn content in GeSn: 300 °C resulted in a Sn content of 2%. These findings are meaningful to researches related to GeSn on insulators for fabricating advanced electrical and optical devices on inexpensive substrates as well as on Si platforms.

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Pseudo single crystal, direct-band-gap Ge0.89Sn0.11 on amorphous dielectric layers towards monolithic 3D photonic integration

Cited by 14 publications

References 24 publications

GeSn on Insulators (GeSnOI) Toward Mid-infrared Integrated Photonics

GeSn on Insulators (GeSnOI) Toward Mid-infrared Integrated Photonics

Ge‐on‐Si Lasers

Sn-inserted Al-induced layer exchange for large-grained GeSn thin films on insulator

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