We measure the time-resolved terahertz spectroscopy of GeSn thin film and studied the ultrafast dynamics of its photo-generated carriers.The experimental results show that there are photo-generated carriers in GeSn un...We measure the time-resolved terahertz spectroscopy of GeSn thin film and studied the ultrafast dynamics of its photo-generated carriers.The experimental results show that there are photo-generated carriers in GeSn under femtosecond laser excitation at 2500 nm,and its pump-induced photoconductivity can be explained by the Drude–Smith model.The carrier recombination process is mainly dominated by defect-assisted Auger processes and defect capture.The firstand second-order recombination rates are obtained by the rate equation fitting,which are(2.6±1.1)×10^(-2)ps^(-1)and(6.6±1.8)×10^(-19)cm^(3)·ps^(-1),respectively.Meanwhile,we also obtain the diffusion length of photo-generated carriers in GeSn,which is about 0.4μm,and it changes with the pump delay time.These results are important for the GeSn-based infrared optoelectronic devices,and demonstrate that Ge Sn materials can be applied to high-speed optoelectronic detectors and other applications.展开更多
An investigation of germanium-tin(GeSn) on silicon p–i–n photodetectors with a high-quality Ge0.94 Sn0.06 absorbing layer is reported. The Ge Sn photodetector reached a responsivity as high as 0.45 A/W at the wavele...An investigation of germanium-tin(GeSn) on silicon p–i–n photodetectors with a high-quality Ge0.94 Sn0.06 absorbing layer is reported. The Ge Sn photodetector reached a responsivity as high as 0.45 A/W at the wavelength of 1550 nm and 0.12 A/W at the wavelength of 2 μm. A cycle annealing technology was applied to improve the quality of the epitaxial layer during the growth process by molecular beam epitaxy. A low dark-current density under 1 V reverse bias about 0.078 A/cm2 was achieved at room temperature. Furthermore, the Ge Sn photodetector could detect a wide spectrum region and the cutoff wavelength reached to about 2.3 μm. This work has great importance in silicon-based short-wave infrared detection.展开更多
Based on the transport equation of the semiconductor device model for 0.524 e V Ge Sn alloy and the experimental parameters of the material,the thermal-electricity conversion performance governed by a Ge Sn diode has ...Based on the transport equation of the semiconductor device model for 0.524 e V Ge Sn alloy and the experimental parameters of the material,the thermal-electricity conversion performance governed by a Ge Sn diode has been systematically studied in its normal and inverted structures.For the normal p^(+)/n(n^(+)/p)structure,it is demonstrated here that an optimal base doping N_(d(a))=3(7)×10^(18)cm^(-3) is observed,and the superior p^(+)/n structure can achieve a higher performance.To reduce material consumption,an economical active layer can comprise a 100 nm-300 nm emitter and a 3μm-6μm base to attain comparable performance to that for the optimal configuration.Our results offer many useful guidelines for the fabrication of economical Ge Sn thermophotovoltaic devices.展开更多
Polycrystalline Ge1-xSnx（poly-Ge1-xSnx） alloy thin films with high Sn content（〉 10%） were fabricated by cosputtering amorphous GeSna-GeSn on Ge100 wafers and subsequently pulsed laser annealing with laser energy ...Polycrystalline Ge1-xSnx（poly-Ge1-xSnx） alloy thin films with high Sn content（〉 10%） were fabricated by cosputtering amorphous GeSna-GeSn on Ge100 wafers and subsequently pulsed laser annealing with laser energy density in the range of 250 mJ/cm^2 to 550 mJ/cm^2. High quality poly-crystal Ge0.90 Sn0.10 and Ge0.82 Sn0.18 films with average grain sizes of 94 nm and 54 nm were obtained, respectively. Sn segregation at the grain boundaries makes Sn content in the poly-GeSn alloys slightly less than that in the corresponding primary a-GeSn. The crystalline grain size is reduced with the increase of the laser energy density or higher Sn content in the primary a-GeSn films due to the booming of nucleation numbers. The Raman peak shift of Ge-Ge mode in the poly crystalline GeSn can be attributed to Sn substitution, strain,and disorder. The dependence of Raman peak shift of the Ge-Ge mode caused by strain and disorder in GeSn films on full-width at half-maximum（FWHM） is well quantified by a linear relationship, which provides an effective method to evaluate the quality of poly-Ge1-xSnx by Raman spectra.展开更多
In this work,a short-wave infrared(SWIR)n-MoSe_(2)/p-GeSn/n-germanium-on-insulator(GOI)heterojunction phototransistor(HPT)with Sn composition-graded GeSn base is proposed for improvement of overall performance at low ...In this work,a short-wave infrared(SWIR)n-MoSe_(2)/p-GeSn/n-germanium-on-insulator(GOI)heterojunction phototransistor(HPT)with Sn composition-graded GeSn base is proposed for improvement of overall performance at low cost.The Sn composition-graded GeSn base layers are grown using magnetron sputtering epitaxy technique for improvement of crystal quality with a high Sn content of 15.2%in the top layer,rendering the extension of the cutoff wavelength beyond 2400 nm and significant suppression of dark current.The enormous electron/hole injection ratio,resulting from the large bandgap offset between the MoSe_(2)emitter and the GeSn base,enables the harvesting of a high photocurrent gain of HPT.By optimizing the device parameters,a considerable responsivity of 23.79 A/W and an excellent specific detectivity of 8.24×10^(10)Jones at the peak wavelength of 2030 nm were achieved for the HPT with the dark current density of 261 mA/cm^(2)under the emitter-collector bias voltage of 1.0 V at room temperature.The fast response speed is obtained for the HPT in terms of rising/falling times of 2.8μs/9.3μs at 1550 nm,surpassing those of most van der Waals(vdW)junction-based devices.Those results demonstrate that GeSn HPTs are suitable for SWIR optoelectronic imaging and microwave photonics applications.展开更多
A GeSn nanostrip grown by the rapid melting growth method has gradient Sn content along the strip,a very attractive approach for making an infrared broad-spectrum light source.In this work,by applying the Sn content d...A GeSn nanostrip grown by the rapid melting growth method has gradient Sn content along the strip,a very attractive approach for making an infrared broad-spectrum light source.In this work,by applying the Sn content distribution strategy.展开更多
We report the demonstration of a normal-incidence p-i-n germanium-tin(Ge_(0.951)Sn_(0.049))photodetector on silicon-on-insulator substrate for 2μm wavelength application.The DC and RF characteristics of the devices h...We report the demonstration of a normal-incidence p-i-n germanium-tin(Ge_(0.951)Sn_(0.049))photodetector on silicon-on-insulator substrate for 2μm wavelength application.The DC and RF characteristics of the devices have been characterized.A dark current density under−1 V bias of approximately 125 mA/cm^(2) is achieved at room temperature,and the optical responsivity of 14 mA/W is realized for illumination wavelength of 2μm under−1 V reverse bias.In addition,a 3 dB bandwidth(f_(3dB))of around 30 GHz is achieved at−3 V,which is the highest reported value among all group III–V and group IV photodetectors working in the 2μm wavelength range.This work illustrates that a GeSn photodetector has great prospects in 2μm wavelength optical communication.展开更多
The GeSn binary alloy is a new group IV material that exhibits a direct bandgap when the Sn content ex- ceeds 6%. It shows great potential for laser use in optoelectronic integration circuits （OEIC） on account of it...The GeSn binary alloy is a new group IV material that exhibits a direct bandgap when the Sn content ex- ceeds 6%. It shows great potential for laser use in optoelectronic integration circuits （OEIC） on account of its low light emission efficiency arising from the indirect bandgap characteristics of Si and Ge. The bandgap of GeSn can be tuned from 0.6 to 0 eV by varying the Sn content, thus making this alloy suitable for use in near-infrared and mid-infrared detectors. In this paper, the growth of the GeSn alloy is first reviewed. Subsequently, GeSn photode- tectors, light emitting diodes, and lasers are discussed. The GeSn alloy presents a promising pathway for the mono- lithic integration of Si photonic circuits by the complementary metal-oxide-semiconductor （CMOS） technology.展开更多
A horizontal p-i-n ridge waveguide emitter on a slion(100)substrate with a Gen,g1Sno.c9/Ge multi quantum-well(MQW)active layer was fabricated by molecular beam epitaxy.The device structure was designed to reduce light...A horizontal p-i-n ridge waveguide emitter on a slion(100)substrate with a Gen,g1Sno.c9/Ge multi quantum-well(MQW)active layer was fabricated by molecular beam epitaxy.The device structure was designed to reduce light absorption of metal electrodes and improve injection efficiency.Electroluminescence(EL)at a wavelength of 2160 nm was observed at room temperature.Theoretical calculations indicate that the emission peak corresponds well to the direct bandgap transition(nr-mHr).The light output power was about 2.0μW with an injection current density of 200 kA/cm^2.These results show that the horizontal GeSn/Ge MQW ridge waveguide emiters have great pros-pects for group-IV light sources.展开更多
GeSn alloys are promising materials for CMOS-compatible mid-infrared lasers manufacturing.Indeed,Sn alloying and tensile strain can transform them into direct bandgap semiconductors.This growing laser technology howev...GeSn alloys are promising materials for CMOS-compatible mid-infrared lasers manufacturing.Indeed,Sn alloying and tensile strain can transform them into direct bandgap semiconductors.This growing laser technology however suffers from a number of limitations,such as poor optical confinement,lack of strain,thermal,and defects management,all of which are poorly discussed in the literature.Herein,a specific GeSn-on-insulator(GeSnOI)stack using stressor layers as dielectric optical claddings is demonstrated to be suitable for a monolithically integration of planar Group-IV semiconductor lasers on a versatile photonic platform for the near-and mid-infrared spectral range.Microdisk-shape resonators on mesa structures were fabricated from GeSnOI,after bonding a Ge_(0.9)Sn_(0.1) alloy layer grown on a Ge strain-relaxed-buffer,itself on a Si(001)substrate.The GeSnOI microdisk mesas exhibited significantly improved optical gain as compared to that of conventional suspended microdisk resonators formed from the as-grown layer.We further show enhanced vertical out-coupling of the disk whispering gallery mode in-plane radiation,with up to 30%vertical out-coupling efficiency.As a result,the GeSnOI approach can be a valuable asset in the development of silicon-based mid-infrared photonics that combine integrated sources in a photonic platform with complex lightwave engineering.展开更多
Despite the recent success of GeSn infrared lasers,the high lasing threshold currently limits their integration into practical applications.While structural defects in epitaxial GeSn layers have been identified as one...Despite the recent success of GeSn infrared lasers,the high lasing threshold currently limits their integration into practical applications.While structural defects in epitaxial GeSn layers have been identified as one of the major bottlenecks towards low-threshold GeSn lasers,the effect of defects on the lasing threshold has not been well studied yet.Herein,we experimentally demonstrate that the reduced defect density in a GeSn-on-insulator substrate improves the lasing threshold significantly.We first present a method of obtaining high-quality GeSn-oninsulator layers using low-temperature direct bonding and chemical–mechanical polishing.Low-temperature photoluminescence measurements reveal that the reduced defect density in GeSn-on-insulator leads to enhanced spontaneous emission and a reduced lasing threshold by0 times andtimes,respectively.Our result presents a new path towards pushing the performance of GeSn lasers to the limit.展开更多
GeSn lasers enable the monolithic integration of lasers on the Si platform using all-group-Ⅳ direct-bandgap material.The GeSn laser study recently moved from optical pumping into electrical injection.In this work,we ...GeSn lasers enable the monolithic integration of lasers on the Si platform using all-group-Ⅳ direct-bandgap material.The GeSn laser study recently moved from optical pumping into electrical injection.In this work,we present explorative investigations of GeSn heterostructure laser diodes with various layer thicknesses and material compositions.Cap layer material was studied by using Si_(0.03)Ge_(0.89)Sn_(0.08) and Ge_(0.95)Sn_(0.05),and cap layer total thickness was also compared.The 190 nm SiGeSn-cap device had threshold of 0.6 kA/cm^(2) at 10 K and a maximum operating temperature(T_(max)) of 100 K,compared to 1.4 kA/cm^(2) and 50 K from 150 nm SiGeSn-cap device,respectively.Furthermore,the 220 nm GeSn-cap device had 10 K threshold at 2.4 kA/cm^(2) and T_(max) at 90 K,i.e.,higher threshold and lower maximal operation temperature compared to the SiGeSn cap layer,indicating that enhanced electron confinement using SiGeSn can reduce the threshold considerably.The study of the active region material showed that device gain region using Ge_(0.87)Sn_(0.13) had a higher threshold and lower T_(max),compared to Ge_(0.89)Sn_(0.11).The performance was affected by the metal absorption,free carrier absorption,and possibly defect density level.The maximum peak wavelength was measured as 2682 nm at 90 K by using Ge_(0.87)Sn_(0.13) in gain regions.The investigations provide directions to the future GeSn laser diode designs toward the full integration of group-Ⅳ photonics on a Si platform.展开更多
The growth of high-quality germanium tin(Ge_(1–y)Sn_(y))binary alloys on a Si substrate using chemical vapor deposition(CVD)techniques holds immense potential for advancing electronics and optoelectronics application...The growth of high-quality germanium tin(Ge_(1–y)Sn_(y))binary alloys on a Si substrate using chemical vapor deposition(CVD)techniques holds immense potential for advancing electronics and optoelectronics applications,including the development of efficient and low-cost mid-infrared detectors and light sources.However,achieving precise control over the Sn concentration and strain relaxation of the Ge_(1–y)Sn_(y)epilayer,which directly influence its optical and electrical properties,remain a significant challenge.In this research,the effect of strain relaxation on the growth rate of Ge_(1–y)Sn_(y)epilayers,with Sn concentration>11at.%,is investigated.It is successfully demonstrated that the growth rate slows down by~55%due to strain relaxation after passing its critical thickness,which suggests a reduction in the incorporation of Ge into Ge_(1–y)Sn_(y)growing layers.Despite the increase in Sn concentration as a result of the decrease in the growth rate,it has been found that the Sn incorporation rate into Ge_(1–y)Sn_(y)growing layers has also decreased due to strain relaxation.Such valuable insights could offer a foundation for the development of innovative growth techniques aimed at achieving high-quality Ge_(1–y)Sn_(y)epilayers with tuned Sn concentration and strain relaxation.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12004067,11974070,62027807,and 52272137)the National Key R&D Program of China(Grant No.2022YFA1403000)。
文摘We measure the time-resolved terahertz spectroscopy of GeSn thin film and studied the ultrafast dynamics of its photo-generated carriers.The experimental results show that there are photo-generated carriers in GeSn under femtosecond laser excitation at 2500 nm,and its pump-induced photoconductivity can be explained by the Drude–Smith model.The carrier recombination process is mainly dominated by defect-assisted Auger processes and defect capture.The firstand second-order recombination rates are obtained by the rate equation fitting,which are(2.6±1.1)×10^(-2)ps^(-1)and(6.6±1.8)×10^(-19)cm^(3)·ps^(-1),respectively.Meanwhile,we also obtain the diffusion length of photo-generated carriers in GeSn,which is about 0.4μm,and it changes with the pump delay time.These results are important for the GeSn-based infrared optoelectronic devices,and demonstrate that Ge Sn materials can be applied to high-speed optoelectronic detectors and other applications.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB2200500)the National Natural Science Foundation of China(Grant Nos.61675195,61934007,and 61974170)+1 种基金Opened Fund of the State Key Laboratory of Integrated Optoelectronics,China(Grant No.IOSKL2018KF17)Beijing Natural Science Foundation,China(Grant No.4162063)
文摘An investigation of germanium-tin(GeSn) on silicon p–i–n photodetectors with a high-quality Ge0.94 Sn0.06 absorbing layer is reported. The Ge Sn photodetector reached a responsivity as high as 0.45 A/W at the wavelength of 1550 nm and 0.12 A/W at the wavelength of 2 μm. A cycle annealing technology was applied to improve the quality of the epitaxial layer during the growth process by molecular beam epitaxy. A low dark-current density under 1 V reverse bias about 0.078 A/cm2 was achieved at room temperature. Furthermore, the Ge Sn photodetector could detect a wide spectrum region and the cutoff wavelength reached to about 2.3 μm. This work has great importance in silicon-based short-wave infrared detection.
基金Project supported by the Beijing Natural Science Foundation Program,China(Grant No.4192016)。
文摘Based on the transport equation of the semiconductor device model for 0.524 e V Ge Sn alloy and the experimental parameters of the material,the thermal-electricity conversion performance governed by a Ge Sn diode has been systematically studied in its normal and inverted structures.For the normal p^(+)/n(n^(+)/p)structure,it is demonstrated here that an optimal base doping N_(d(a))=3(7)×10^(18)cm^(-3) is observed,and the superior p^(+)/n structure can achieve a higher performance.To reduce material consumption,an economical active layer can comprise a 100 nm-300 nm emitter and a 3μm-6μm base to attain comparable performance to that for the optimal configuration.Our results offer many useful guidelines for the fabrication of economical Ge Sn thermophotovoltaic devices.
基金Project supported by the National Natural Science Foundation of China(Grant No.61474094)the National Basic Research Program of China(Grant No.2013CB632103)
文摘Polycrystalline Ge1-xSnx（poly-Ge1-xSnx） alloy thin films with high Sn content（〉 10%） were fabricated by cosputtering amorphous GeSna-GeSn on Ge100 wafers and subsequently pulsed laser annealing with laser energy density in the range of 250 mJ/cm^2 to 550 mJ/cm^2. High quality poly-crystal Ge0.90 Sn0.10 and Ge0.82 Sn0.18 films with average grain sizes of 94 nm and 54 nm were obtained, respectively. Sn segregation at the grain boundaries makes Sn content in the poly-GeSn alloys slightly less than that in the corresponding primary a-GeSn. The crystalline grain size is reduced with the increase of the laser energy density or higher Sn content in the primary a-GeSn films due to the booming of nucleation numbers. The Raman peak shift of Ge-Ge mode in the poly crystalline GeSn can be attributed to Sn substitution, strain,and disorder. The dependence of Raman peak shift of the Ge-Ge mode caused by strain and disorder in GeSn films on full-width at half-maximum（FWHM） is well quantified by a linear relationship, which provides an effective method to evaluate the quality of poly-Ge1-xSnx by Raman spectra.
基金supported in part by the National Natural Science Foundation of China(Nos.62074134 and 62104205)in part by the National Key Research and Development Program of China(No.2018YFB2200103).
文摘In this work,a short-wave infrared(SWIR)n-MoSe_(2)/p-GeSn/n-germanium-on-insulator(GOI)heterojunction phototransistor(HPT)with Sn composition-graded GeSn base is proposed for improvement of overall performance at low cost.The Sn composition-graded GeSn base layers are grown using magnetron sputtering epitaxy technique for improvement of crystal quality with a high Sn content of 15.2%in the top layer,rendering the extension of the cutoff wavelength beyond 2400 nm and significant suppression of dark current.The enormous electron/hole injection ratio,resulting from the large bandgap offset between the MoSe_(2)emitter and the GeSn base,enables the harvesting of a high photocurrent gain of HPT.By optimizing the device parameters,a considerable responsivity of 23.79 A/W and an excellent specific detectivity of 8.24×10^(10)Jones at the peak wavelength of 2030 nm were achieved for the HPT with the dark current density of 261 mA/cm^(2)under the emitter-collector bias voltage of 1.0 V at room temperature.The fast response speed is obtained for the HPT in terms of rising/falling times of 2.8μs/9.3μs at 1550 nm,surpassing those of most van der Waals(vdW)junction-based devices.Those results demonstrate that GeSn HPTs are suitable for SWIR optoelectronic imaging and microwave photonics applications.
基金National Key Research and Development Program of China(2022YFB2803100)National Natural Science Foundation of China(62090054,62274160,62404216).
文摘A GeSn nanostrip grown by the rapid melting growth method has gradient Sn content along the strip,a very attractive approach for making an infrared broad-spectrum light source.In this work,by applying the Sn content distribution strategy.
文摘在Si(001)衬底上,以高质量的弛豫Ge薄膜作为缓冲层,先后生长Sn组分x分别为2.5%,5.2%和7.8%的完全应变的三层Ge_(1-x)Sn_x合金薄膜.在Si(001)衬底上直接生长了x分别为0.005,0.016,0.044,0.070和0.155的五个弛豫Ge_(1-x)Sn_x样品.通过卢瑟福背散射谱、高分辨X射线衍射和X射线倒易空间图等方法测量了Ge_(1-x)Sn_x合金的组分与晶格常数.实验得到的晶格常数相对Vegard定律具有较大的正偏离,弯曲系数b=0.211 A.
基金National Natural Science Foundation of China(61774143,61874109,61975121,61975196)National Key Research and Development Program of China(2018YFB2200501,2019YFB2203400).
文摘We report the demonstration of a normal-incidence p-i-n germanium-tin(Ge_(0.951)Sn_(0.049))photodetector on silicon-on-insulator substrate for 2μm wavelength application.The DC and RF characteristics of the devices have been characterized.A dark current density under−1 V bias of approximately 125 mA/cm^(2) is achieved at room temperature,and the optical responsivity of 14 mA/W is realized for illumination wavelength of 2μm under−1 V reverse bias.In addition,a 3 dB bandwidth(f_(3dB))of around 30 GHz is achieved at−3 V,which is the highest reported value among all group III–V and group IV photodetectors working in the 2μm wavelength range.This work illustrates that a GeSn photodetector has great prospects in 2μm wavelength optical communication.
基金Project supported by the Beijing Natural Science Foundation(No.4162063)the Youth Innovation Promotion Association of CAS(No.2015091)
文摘The GeSn binary alloy is a new group IV material that exhibits a direct bandgap when the Sn content ex- ceeds 6%. It shows great potential for laser use in optoelectronic integration circuits （OEIC） on account of its low light emission efficiency arising from the indirect bandgap characteristics of Si and Ge. The bandgap of GeSn can be tuned from 0.6 to 0 eV by varying the Sn content, thus making this alloy suitable for use in near-infrared and mid-infrared detectors. In this paper, the growth of the GeSn alloy is first reviewed. Subsequently, GeSn photode- tectors, light emitting diodes, and lasers are discussed. The GeSn alloy presents a promising pathway for the mono- lithic integration of Si photonic circuits by the complementary metal-oxide-semiconductor （CMOS） technology.
基金National Key Research and Development Program(2018YFB2200103,2018YFB2200501)National Natural Science Foundation of China(61674140,61675195,61774143,61975196)Key Research Program of Frontier Sciences(QYZDY-SSW-JSC022).
文摘A horizontal p-i-n ridge waveguide emitter on a slion(100)substrate with a Gen,g1Sno.c9/Ge multi quantum-well(MQW)active layer was fabricated by molecular beam epitaxy.The device structure was designed to reduce light absorption of metal electrodes and improve injection efficiency.Electroluminescence(EL)at a wavelength of 2160 nm was observed at room temperature.Theoretical calculations indicate that the emission peak corresponds well to the direct bandgap transition(nr-mHr).The light output power was about 2.0μW with an injection current density of 200 kA/cm^2.These results show that the horizontal GeSn/Ge MQW ridge waveguide emiters have great pros-pects for group-IV light sources.
基金This work was supported by the French RENATECH network,the French National Research Agency(Agence Nationale de la Recherche,ANR)through funding of the ELEGANTE project(ANR-17-CE24-0015)B.W.was supported by Nano2022 IPCEI project with STMicroelectronics.
文摘GeSn alloys are promising materials for CMOS-compatible mid-infrared lasers manufacturing.Indeed,Sn alloying and tensile strain can transform them into direct bandgap semiconductors.This growing laser technology however suffers from a number of limitations,such as poor optical confinement,lack of strain,thermal,and defects management,all of which are poorly discussed in the literature.Herein,a specific GeSn-on-insulator(GeSnOI)stack using stressor layers as dielectric optical claddings is demonstrated to be suitable for a monolithically integration of planar Group-IV semiconductor lasers on a versatile photonic platform for the near-and mid-infrared spectral range.Microdisk-shape resonators on mesa structures were fabricated from GeSnOI,after bonding a Ge_(0.9)Sn_(0.1) alloy layer grown on a Ge strain-relaxed-buffer,itself on a Si(001)substrate.The GeSnOI microdisk mesas exhibited significantly improved optical gain as compared to that of conventional suspended microdisk resonators formed from the as-grown layer.We further show enhanced vertical out-coupling of the disk whispering gallery mode in-plane radiation,with up to 30%vertical out-coupling efficiency.As a result,the GeSnOI approach can be a valuable asset in the development of silicon-based mid-infrared photonics that combine integrated sources in a photonic platform with complex lightwave engineering.
基金Mitacs,Innovation for Defence Excellence and Security,IDEaS,PRIMA Québec,Canada Foundation for Innovation,Canada Research Chairs,Natural Sciences and Engineering Research Council of Canada,iGrant of Singapore A*STAR(AME IRG(A2083c0053))National Research Foundation Singapore(Competitive Research Program(NRF-CRP19-2017-01)+3 种基金NRF-ANR Joint Grant(NRF2018-NRF-ANR009 TIGER))Ministry of Education-Singapore(Ac RF TIER 12019-T1-002-050(RG 148/19(S))AcRF TIER 2(MOE2018-T2-2-011(S))AcRF Tier 2(T2EP50121-0001(MOE-000180-01))。
文摘Despite the recent success of GeSn infrared lasers,the high lasing threshold currently limits their integration into practical applications.While structural defects in epitaxial GeSn layers have been identified as one of the major bottlenecks towards low-threshold GeSn lasers,the effect of defects on the lasing threshold has not been well studied yet.Herein,we experimentally demonstrate that the reduced defect density in a GeSn-on-insulator substrate improves the lasing threshold significantly.We first present a method of obtaining high-quality GeSn-oninsulator layers using low-temperature direct bonding and chemical–mechanical polishing.Low-temperature photoluminescence measurements reveal that the reduced defect density in GeSn-on-insulator leads to enhanced spontaneous emission and a reduced lasing threshold by0 times andtimes,respectively.Our result presents a new path towards pushing the performance of GeSn lasers to the limit.
基金Air Force Office of Scientific Research (FA9550-18-1-0045, FA9550-19-1-0341, FA9550-21-1-0347)。
文摘GeSn lasers enable the monolithic integration of lasers on the Si platform using all-group-Ⅳ direct-bandgap material.The GeSn laser study recently moved from optical pumping into electrical injection.In this work,we present explorative investigations of GeSn heterostructure laser diodes with various layer thicknesses and material compositions.Cap layer material was studied by using Si_(0.03)Ge_(0.89)Sn_(0.08) and Ge_(0.95)Sn_(0.05),and cap layer total thickness was also compared.The 190 nm SiGeSn-cap device had threshold of 0.6 kA/cm^(2) at 10 K and a maximum operating temperature(T_(max)) of 100 K,compared to 1.4 kA/cm^(2) and 50 K from 150 nm SiGeSn-cap device,respectively.Furthermore,the 220 nm GeSn-cap device had 10 K threshold at 2.4 kA/cm^(2) and T_(max) at 90 K,i.e.,higher threshold and lower maximal operation temperature compared to the SiGeSn cap layer,indicating that enhanced electron confinement using SiGeSn can reduce the threshold considerably.The study of the active region material showed that device gain region using Ge_(0.87)Sn_(0.13) had a higher threshold and lower T_(max),compared to Ge_(0.89)Sn_(0.11).The performance was affected by the metal absorption,free carrier absorption,and possibly defect density level.The maximum peak wavelength was measured as 2682 nm at 90 K by using Ge_(0.87)Sn_(0.13) in gain regions.The investigations provide directions to the future GeSn laser diode designs toward the full integration of group-Ⅳ photonics on a Si platform.
文摘The growth of high-quality germanium tin(Ge_(1–y)Sn_(y))binary alloys on a Si substrate using chemical vapor deposition(CVD)techniques holds immense potential for advancing electronics and optoelectronics applications,including the development of efficient and low-cost mid-infrared detectors and light sources.However,achieving precise control over the Sn concentration and strain relaxation of the Ge_(1–y)Sn_(y)epilayer,which directly influence its optical and electrical properties,remain a significant challenge.In this research,the effect of strain relaxation on the growth rate of Ge_(1–y)Sn_(y)epilayers,with Sn concentration>11at.%,is investigated.It is successfully demonstrated that the growth rate slows down by~55%due to strain relaxation after passing its critical thickness,which suggests a reduction in the incorporation of Ge into Ge_(1–y)Sn_(y)growing layers.Despite the increase in Sn concentration as a result of the decrease in the growth rate,it has been found that the Sn incorporation rate into Ge_(1–y)Sn_(y)growing layers has also decreased due to strain relaxation.Such valuable insights could offer a foundation for the development of innovative growth techniques aimed at achieving high-quality Ge_(1–y)Sn_(y)epilayers with tuned Sn concentration and strain relaxation.
