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Characteristics of GeSn-based multiple quantum well heterojunction phototransistors: a simulation-based analysis
摘要： Introduction of multiple quantum wells (MQWs) is an efficient way to enhance the light absorption capability in phototransistors. Direct band gap Ge1?xSnx alloy (x?>?0.08) having large absorption coefficient is an attractive material for heterojunction phototransistors (HPTs) compatible with CMOS platform. In this work, simulations are employed to obtain current gain, responsivity and collector current characteristics of Ge/GeSn/Ge HPTs with incorporation of MQWs (Ge0.87Sn0.13/Ge0.83Sn0.17) in the base region. The performances of bulk, single quantum well and MQW HPT structures are examined and compared. Best performance is shown by HPTs having MQW structure over a wide range of base emitter voltage.
关键词： simulation,current gain,heterojunction phototransistors,responsivity,GeSn,multiple quantum wells
更新于2025-09-23 15:21:21
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[IEEE 2018 IEEE Symposium on VLSI Technology - Honolulu, HI, USA (2018.6.18-2018.6.22)] 2018 IEEE Symposium on VLSI Technology - Metal/P-type GeSn Contacts with Specific Contact Resistivity down to 4.4×10 <sup>?10</sup> Ω-cm <sup>2</sup>
摘要： Ga and Sn surface-segregated p+-GeSn (Seg. p+-GeSn) was grown by molecular beam epitaxy (MBE) to achieve an average active Ga doping concentration of 3.4×1020 cm-3 and surface Sn composition of more than 8%. This enables the realization of record-low specific contact resistivity ρc down to 4.4×10-10 ?-cm2. The average ρc extracted from 14 sets of Ti/Seg. p+-GeSn Nano-TLM test structures, a collection of more than 90 devices is 6.5×10-10 ?-cm2. This is also the lowest ρc for non-laser-annealed contacts. Ti contacts to p+-GeSn films with and without Ga and Sn surface segregation were fabricated. It is shown that the segregation of Ga and Sn at the Ti/p+-GeSn interface leads to 50% reduction in ρc as compared with a sample without segregation.
关键词： Ga and Sn surface-segregated p+-GeSn,molecular beam epitaxy,specific contact resistivity,Nano-TLM test structures
更新于2025-09-23 15:21:21
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Design of a Si-based Lattice-matched GeSn/SiGeSn Multi-quantum-well Laser
摘要： By calculating the heterojunction band alignment of GeSn/SiGeSn, a Ge0.9Sn0.1/Si0.14Ge0.71Sn0.15 multi-quantum-well laser was designed, where three Ge0.9Sn0.1 layers act as wells separated by three Si0.14Ge0.71Sn0.15 layers as barriers. The maximum TE gain reaches 7000 cm?1 at 0.5 eV, and the maximum TM gain reaches 5500 cm?1 at 0.52 eV. The modal gain of the Ge0.9Sn0.1/Si0.14Ge0.71Sn0.15 multi-quantum-well laser we proposed and designed can reach 100 cm?1 with a current density of 5 kA/cm2. The result indicates that it is possible to obtain a Si-based laser.
关键词： GeSn/SiGeSn laser,multi-quantum-well laser,Si-based laser
更新于2025-09-23 15:19:57
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Direct-indirect GeSn band structure formation by laser Radiation: The enhancement of Sn solubility in Ge
摘要： Low equilibrium solid solubility of Sn atoms in Ge (less than 1%) leads to limitations in application of this material for IR detectors and emitters. Providing of non-equilibrium conditions by powerful pulsed laser radiation can be successfully applied for enhancement of solubility of impurity atoms in the host material. Here we present laser-induced monotonous redistribution of Sn atoms in Ge, based on the thermogradient effect aiming overcoming equilibrium limitations in the solubility. We applied pulsed nanosecond laser radiation to epitaxial Ge0.96Sn0.04 layer grown on Si substrate to increase Sn atomic concentration up to 14% at the surface layer. As a result, indirect-direct graded bandgap GeSn structure was formed. The TEM/EDS cross-section analysis, X-ray photoelectron spectroscopy, Raman and UV reflection spectra confirmed the increase of Sn atomic content at the surface by order of magnitude. SEM and AFM imaging provided evident microstructure changes, while carrier lifetime changes, determined by differential transmittivity, were not observed, indicating that laser irradiation does not generate defects which reduce electronic quality of the material.
关键词： Laser radiation,Thermogradient effect,Solid solution,Carrier recombination,GeSn
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Toward Monolithic Optoelectronic Integration of GeSn Photodiode and FinFET on GeSnOI Platform
摘要： We demonstrated a GeSn-on-insulator platform for monolithic optoelectronic integration for applications at 2 μm wavelength. Both GeSn lateral p-i-n photodetector and p-channel fin field-effect transistor were realized using this novel architecture.
关键词： optoelectronic integration,2 μm,GeSn
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Investigation of Resonant-Cavity-Enhanced GeSn Photodetectors in Short-Wavelength Infrared Regime
摘要： GeSn with a 10% Sn content for resonant-cavity-enhanced photodetectors (RCE PDs) was grown and the RCE PDs was designed for 2000-nm operation, exhibiting a quantum efficiency up to 91%. This work shows RCE GeSn PDs can be a promising route toward high-response SWIR detection.
关键词： quantum efficiency,Resonant-cavity-enhanced photodetectors,GeSn
更新于2025-09-16 10:30:52
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Materials physics of GeSn-based semiconductor lasers
摘要： Optically pumped Ge1-ySny lasers operating at low temperature have been recently demonstrated. This article reviews the challenges to efficient lasing that arise from the intrinsic properties of alloys in the Si-Ge-Sn system. The first such challenge is the possibility that even in nominally direct gap Ge1-ySny materials, a significant fraction of pumped carriers reside in the valleys associated with the indirect gap, and therefore are not available for lasing. We find theoretically that this is indeed the case at room temperature, possibly explaining the strong temperature dependence of lasing. A second challenge is finding appropriate barrier materials to reduce the lasing threshold power via spatial confinement. We show that strained layer Ge1-ySny/Ge1-y?Sny? multilayers are unlikely to produce the required direct gap Type-I alignment, and that even the introduction of ternary Ge1-x- ySixSny layers may not lead to suitable lasing structures due to giant bowing parameters in the compositional dependences of their interband transition energies.
关键词： SiGeSn,lasers,GeSn
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - GeSn Lasers with Uniaxial Tensile Strain in the Gain Medium
摘要： We use strain redistribution to locally enhance strain in GeSn layers. We demonstrate uniaxial tensile strain in microbridges with lasing cavities tuned over the 3.1 to 4.6μm range, and thresholds lower than 10 kW.cm-2 at 25K, in pulsed excitation mode. Laser operation vanishes around 273K.
关键词： laser,strain,tunability,GeSn
更新于2025-09-16 10:30:52
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Si-based GeSn photodetectors towards mid-infrared imaging applications
摘要： The GeSn detector offers the high-performance Si-based infrared photodetectors with complementary metal-oxide-semiconductor (CMOS) technique compatibility. In this work, we reports a comprehensive study of Si-based GeSn mid-infrared photodetectors, which includes: i) the demonstration of a set of photoconductors with Sn compositions ranging from 10.5% to 22.3%, showing the cut-off wavelength has been extended to 3.65 μm. The maximum D* of 1.1×1010 cm?Hz1/2?W-1 measured at 77 K is comparable to that of commercial extended-InGaAs detectors; ii) the development of surface passivation technique on photodiode based on in-depth analysis of dark current mechanism, effectively reducing the dark current. Moreover, mid-infrared images were obtained using GeSn photodetectors, showing the comparable image quality with that acquired by using commercial PbSe detectors. This work is a major step towards Si-based mid-infrared photodetectors for imaging applications.
关键词： surface passivation,GeSn photodetector,high Sn composition,imaging,mid-infrared
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Investigation of Resonant-Cavity-Enhanced GeSn Photodetectors in Short-Wavelength Infrared Regime
摘要： GeSn with a 10% Sn content for resonant-cavity-enhanced photodetectors (RCE PDs) was grown and the RCE PDs was designed for 2000-nm operation, exhibiting a quantum efficiency up to 91%. This work shows RCE GeSn PDs can be a promising route toward high-response SWIR detection.
关键词： Resonant-cavity-enhanced photodetectors,quantum efficiency,GeSn
更新于2025-09-12 10:27:22