Enhanced photoluminescence of GeSn by strain relaxation and spontaneous carrier confinement through rapid thermal annealing

Lin, Guoxing; Qian, Kun; Cai, Hongjie; Zhao, Huichang; Xu, Jianfang; Chen, Songyan; Li, Cheng; Hickey, Ryan; Kolodzey, J.; Zeng, Yuping

doi:10.1016/j.jallcom.2022.165453

Cited by 11 publications

(6 citation statements)

References 52 publications

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“…Figure 1(d) shows the PL spectra of the GeSn sample before (upper panel) and after (lower panel) RTA measured at room temperature, respectively. The broad PL spectra are originated from the following four contributions [ 40 ]: direct bandgap radiation of Ge (P1), direct bandgap radiation of GeSn (P2), 2nd order diffraction of pumping laser by grating fixing at ∼2125 nm (P3) and indirect bandgap emission of GeSn (P4). Detailed analysis of PL spectra can be found in the Supplementary Material .…”

Section: Resultsmentioning

confidence: 99%

Scalable fabrication of self-assembled GeSn vertical nanowires for nanophotonic applications

Lin

Ding

et al. 2023

Nanophotonics

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In this work, scalable fabrication of self-assembled GeSn vertical nanowires (NWs) based on rapid thermal annealing (RTA) and inductively coupled-plasma (ICP) dry etching was proposed. After thermal treatment of molecular-beam-epitaxy-grown GeSn, self-assembled Sn nanodots (NDs) were formed on surface and the spontaneous emission from GeSn direct band was enhanced by ∼5-fold. Employing the self-assembled Sn NDs as template, vertical GeSn NWs with a diameter of 25 ± 6 nm and a density of 2.8 × 109 cm−2 were obtained by Cl-based ICP dry etching technique. A prototype GeSn NW photodetector (PD) with rapid switching ability was demonstrated and the optoelectronic performance of Ge NW PD was systematically studied. The GeSn NW PD exhibited an ultralow dark current density of ∼33 nA/cm2 with a responsivity of 0.245 A/W and a high specific detectivity of 2.40 × 1012 cm Hz1/2 W−1 at 1550 nm under −1 V at 77 K. The results prove that this method is prospective for low-cost and scalable fabrication of GeSn NWs, which are promising for near infrared or short wavelength infrared nanophotonic devices.

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Section: Resultsmentioning

confidence: 99%

Scalable fabrication of self-assembled GeSn vertical nanowires for nanophotonic applications

Lin

Ding

et al. 2023

Nanophotonics

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“…Figure 2(B) shows the asymmetric ( 22 4) XRD reciprocal space mapping (RSM) of the sample grown at 405 • C. The vertical alignment of GeSn and Ge VS peaks indicates that the GeSn film and Ge VS have an equal in-plane lattice constant. Thus, GeSn is fully strained to Ge VS. Based on the peak separation between GeSn and Ge VS, the Sn content of the GeSn film is calculated as 6.2% [26]. For the sample grown at 388 • C, from the asymmetric ( 22 4) XRD-RSM (not shown), the GeSn film is also verified to be fully strained on Ge VS with a Sn content of 6.2%.…”

Section: Figures 1(a)-(d) Display the Surface Morphology Of Ge Vsmentioning

confidence: 99%

“…and normalized for comparison, as presented by the black curve in figure 5. The MBE-grown GeSn, which has a Sn content of 6.6% and a thickness of 200 nm [26], is obtained at a growth temperature of 150 • C. The PL peak of MBE-grown GeSn is located at around 2000 nm. The shorter wavelength of the emission peak for sputtering-grown GeSn compared to that for MBE-grown GeSn with similar Sn content may be due to short-range order of GeSn grown by high-temperature sputtering, which is energy favorable to achieve the relaxation state of GeSn unit cell [37], i.e.…”

Section: Figures 1(a)-(d) Display the Surface Morphology Of Ge Vsmentioning

confidence: 99%

“…Although Sn-rich GeSn can be obtained, the low-temperature deposition process results in kinetic roughing of the GeSn surface, which gradually leads to epitaxy breakdown [15] and/or hinders relaxation of the compressive strain in the GeSn film [16]. For these reasons, efficient light emission of MBE-grown GeSn is still under development [25][26][27]. Sputtering is another common PVD technique.…”

Section: Introductionmentioning

confidence: 99%

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Harvesting strong photoluminescence of physical vapor deposited GeSn with record high deposition temperature

Lin

Qian

Ding

et al. 2023

J. Phys. D: Appl. Phys.

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In this work, strong photoluminescence (PL) from physical vapor deposited GeSn on Ge-buffered Si is harvested by pursuing high deposition temperature. High-quality Ge0.938Sn0.062 film is obtained through sputtering epitaxy at a record high temperature of 405oC. The PL peak intensity of the sputtering-grown GeSn is enhanced by 21 times compared to that of GeSn with similar Sn content grown by molecular beam epitaxy at 150oC. The PL intensity ratio between the sputtering-grown GeSn and Ge virtual substrate (VS) reaches a value of 18. Power-dependent and temperature-dependent PL characterizations demonstrate that band-to-band recombination dominates in the sputtering-grown GeSn film. The results indicate that high-temperature sputtering epitaxy, which has a merit of low cost and high-productivity potential, is promising to prepare high-quality GeSn films for optoelectronic applications.

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“…Recently, we demonstrate that compressive strain in GeSn thin films grown by MBE can be relaxed by rapid thermal annealing when the thickness of GeSn satisfies the temperature-dependent critical values [28,29]. In that case, the strain relaxation of GeSn thin films is driven by generation of misfit dislocations during thermal treatments without Sn surface segregation.…”

Section: Introductionmentioning

confidence: 99%

Secondary epitaxy of high Sn fraction GeSn layer on strain-relaxed GeSn virtue substrate by molecular beam epitaxy

Qian¹,

Wu²,

Qian³

et al. 2023

J. Phys. D: Appl. Phys.

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Strain relaxation is critical for GeSn alloys transforming from indirect to direct bandgap nature with Sn fraction above 6.5%, but difficult for them grown by molecular beam epitaxy, in which low temperature has to be set up to avoid Sn segregation. In this work, compressively strained Ge0.935Sn0.065 thin films grown on Si with a Ge buffer layer by molecular beam epitaxy are firstly treated by ex-situ rapid thermal annealing, rendering partially strain relaxation in the Ge0.935Sn0.065 by generation of misfit dislocation networks without Sn segregation. Then, secondary epitaxy of Ge0.905Sn0.095 layer is carried out on the thermally annealed Ge0.935Sn0.065 virtual substrate. The secondary epitaxial GeSn layers exhibit partial strain relaxation and strong photoluminescence with red-shift of peak position, compared to that of fully compressive strained GeSn thin films with the same structure grown primary epitaxially. Those results manifest that secondary epitaxy, combining with ex-situ rapid thermal annealing for strain relaxed GeSn virtual substrate, is a practical way to achieve strain relaxed GeSn thin films with direct bandgap nature by molecular beam epitaxy.

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Enhanced photoluminescence of GeSn by strain relaxation and spontaneous carrier confinement through rapid thermal annealing

Cited by 11 publications

References 52 publications

Scalable fabrication of self-assembled GeSn vertical nanowires for nanophotonic applications

Scalable fabrication of self-assembled GeSn vertical nanowires for nanophotonic applications

Harvesting strong photoluminescence of physical vapor deposited GeSn with record high deposition temperature

Secondary epitaxy of high Sn fraction GeSn layer on strain-relaxed GeSn virtue substrate by molecular beam epitaxy

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