High-performance Ge-on-insulator lateral p-i-n waveguide photodetectors for electronic-photonic integrated circuits at telecommunication wavelengths.

We report high-performance germanium-on-insulator (GeOI) waveguide photodetectors (WGPDs) for electronic-photonic integrated circuits (EPICs) operating at telecommunication wavelengths. The GeOI samples were fabricated using layer transfer and wafer-bonding techniques, and a high-quality Ge active layer was achieved. Planar lateral p-i-n WGPDs were fabricated and characterized, and they exhibited a low dark current of 0.1 µA. Strain-induced alterations in the optical properties were observed, resulting in an extended photodetection range up to λ = 1638 nm. This range encompasses crucial telecommunication bands. The WGPDs exhibited a high responsivity of 0.56 A/W and a high detectivity of D ∗ = 1.87 ×109cmHz1/2W - 1 at 1550 nm. A frequency-response analysis revealed that increasing the bias voltage from -1 to -9 V enhances the 3-dB bandwidth from 31 to 49 MHz. This study offers a comprehensive understanding of GeOI WGPDs, fostering high-performance EPICs with implications for telecommunications and beyond.

Enhanced light emission of germanium light-emitting-diode on 150 mm germanium-on-insulator (GOI).

Germanium-on-insulator (GOI) has emerged as a novel platform for Ge-based electronic and photonic applications. Discrete photonic devices, such as waveguides, photodetectors, modulators, and optical pumping lasers, have been successfully demonstrated on this platform. However, there is almost no report on the electrically injected Ge light source on the GOI platform. In this study, we present the first fabrication of vertical Ge p-i-n light-emitting diodes (LEDs) on a 150 mm GOI substrate. The high-quality Ge LED on a 150-mm diameter GOI substrate was fabricated via direct wafer bonding followed by ion implantations. As a tensile strain of 0.19% has been introduced during the GOI fabrication process resulting from the thermal mismatch, the LED devices exhibit a dominant direct bandgap transition peak near 0.785 eV (∼1580 nm) at room temperature. In sharp contrast to conventional III-V LEDs, we found that the electroluminescence (EL)/photoluminescence (PL) spectra show enhanced intensities as the temperature is raised from 300 to 450 K as a consequence of the higher occupation of the direct bandgap. The maximum enhancement in EL intensity is a factor of 140% near 1635 nm due to the improved optical confinement offered by the bottom insulator layer. This work potentially broadens the GOI's functional variety for applications in near-infrared sensing, electronics, and photonics.

Grating and hole-array enhanced germanium lateral p-i-n photodetectors on an insulator platform.

Germanium (Ge) lateral p-i-n photodetectors with grating and hole-array structures were fabricated on a Ge-on-insulator (GOI) platform. Owing to the low threading dislocation density (TDD) in the transferred Ge layer, a low dark current of 0.279 µA was achieved at -1 V. The grating structure enhances the optical absorption by guiding the lateral propagation of normal incident light, contributing to a 3× improved responsivity at 1,550 nm. Compared with the grating structure, the hole-array structure not only guides the lateral modes but also benefits the vertical resonance modes. A 4.5× higher responsivity of 0.188 A/W at 1,550 nm was achieved on the 260 nm Ge absorptive layer. In addition, both the grating and the hole-array structure attribute to a 2× and a 1.6× enhanced 3dB bandwidth at -5 V due to significantly reduced capacitance. The planar configuration of p-i-n photodiodes is favorable for large-scale monolithic integration. The incorporated surface structures offer promising approaches to reinforce the responsivity and bandwidth simultaneously, paving the way for the development of high-performance Ge photodetectors on silicon substrate.

Surface plasmon enhanced GeSn photodetectors operating at 2 µm.

Au-hole array and Au-GeSn grating structures were designed and incorporated in GeSn metal-semiconductor-metal (MSM) photodetectors for enhanced photo detection at 2 µm. Both plasmonic structures are beneficial for effective optical confinement near the surface due to surface plasmon resonance (SPR), contributing to an enhanced responsivity. The responsivity enhancement for Au hole-array structure is insensitive to the polarization direction, while the enhancement for Au-GeSn grating structure depends on the polarization direction. The responsivity for GeSn photodetector with Au hole-array structure has ∼50% reinforcement compared with reference photodetector. On the other hand, Au-GeSn grating structure benefits a 3× enhanced responsivity of 0.455 A/W at 1.5V under TM-polarized illumination. The achieved responsivity is among the highest values for GeSn photodetectors operating at 2 µm. The plasmonic GeSn photodetectors in this work offer an alternative solution for high-efficiency photo detection, manifesting their great potentials as candidates for 2 µm optical communication and other emerging applications.

GeSn-on-insulator dual-waveband resonant-cavity-enhanced photodetectors at the 2 µm and 1.55 µm optical communication bands.

Germanium-tin-on-insulator (GSOI) has emerged as a new platform for three-dimensional (3D) photonic-integrated circuits (PICs). We report, to our knowledge, the first demonstration of GeSn dual-waveband resonant-cavity-enhanced photodetectors (RCE PDs) on GSOI platforms with resonance-enhanced responsivity at both 2 µm and 1.55 µm bands. 10% Sn is introduced to the GeSn absorbing layer to extend the detection wavelength to the 2 µm band. A vertical Fabry-Perot cavity is designed to enhance the responsivity. The measured responsivity spectra show resonance peaks that cover a wide wavelength range near both the 2 µm and conventional telecommunication bands. This work demonstrates that GeSn dual-waveband RCE PDs on a GSOI platform are promising for CMOS-compatible 3D PICs for optoelectronic applications in 2 µm and telecommunication bands.

Resonant-cavity-enhanced responsivity in germanium-on-insulator photodetectors.

The germanium-on-insulator (GOI) has recently emerged as a new platform for complementary metal-oxide-semiconductor (CMOS)-compatible photonic integrated circuits. Here we report on resonant-cavity-enhanced optical responses in Ge photodetectors on a GOI platform where conventional photodetection is difficult. A 0.16% tensile strain is introduced to the high-quality Ge active layer to extend the photodetection range to cover the entire range of telecommunication C- and L-bands (1530-1620 nm). A carefully designed vertical cavity is created utilizing the insulator layer and the deposited SiO2 layer to enhance the optical confinement and thus optical response near the direct-gap absorption edge. Experimental results show a responsivity peak at 1590 nm, confirming the resonant cavity effect. Theoretical analysis shows that the optical responsivity in the C- and L-bands is significantly enhanced. Thus, we have demonstrated a new type of Ge photodetector on a GOI platform for CMOS-compatible photonic integrated circuits for telecommunication applications.

High-efficiency GeSn/Ge multiple-quantum-well photodetectors with photon-trapping microstructures operating at 2 µm.

We introduced photon-trapping microstructures into GeSn-based photodetectors for the first time, and achieved high-efficiency photo detection at 2 µm with a responsivity of 0.11 A/W. The demonstration was realized by a GeSn/Ge multiple-quantum-well (MQW) p-i-n photodiode on a GeOI architecture. Compared with the non-photon-trapping counterparts, the patterning and etching of photon-trapping microstructure can be processed in the same step with mesa structure at no additional cost. A four-fold enhancement of photo response was achieved at 2 µm. Although the incorporation of photo-trapping microstructure degrades the dark current density which increases from 31.5 to 45.2 mA/cm2 at -1 V, it benefits an improved 3-dB bandwidth of 2.7 GHz at bias voltage at -5 V. The optical performance of GeSn/Ge MQW photon-trapping photodetector manifests its great potential as a candidate for efficient 2 µm communication. Additionally, the underlying GeOI platform enables its feasibility of monolithic integration with other photonic components such as waveguide, modulator and (de)multiplexer for optoelectronic integrated circuits (OEICs) operating at 2 µm.

Wafer-scale nanostructured black silicon with morphology engineering via advanced Sn-assisted dry etching for sensing and solar cell applications.

Black-Si (b-Si) providing broadband light antireflection has become a versatile substrate for photodetectors, photo-electric catalysis, sensors, and photovoltaic devices. However, the conventional fabrication methods suffer from single morphology, low yield, or frangibility. In this work, we present a high-yield CMOS-compatible technique to produce 6-inch wafer-scale b-Si with diverse random nanostructures. b-Si is achieved by O2/SF6 plasma-based reactive ion etching (RIE) of the Si wafer which is coated with a GeSn layer. A stable grid of the SnOxFy layer, formed during the initial GeSn etching, acts as a self-assembled hard mask for the formation of subwavelength Si nanostructures. b-Si wafers with diverse surface morphologies, such as the nanopore, nanocone, nanohole, nanohillock, and nanowire were achieved. Furthermore, the responsivity of the b-Si metal-semiconductor-metal (MSM) photodetector in the near-infrared (NIR) wavelength range (1000-1200 nm) is 40-200% higher than that of a planar-Si MSM photodetector with the same level of dark current, which is beneficial for applications in photon detectors, solar cells, and photocatalysis. This work not only demonstrates a new non-lithography method to fabricate wafer-scale b-Si wafers, but may also provide a novel strategy to fabricate other nanostructured surface materials (e.g., Ge or III-V based compounds) with morphology engineering.

A Route toward High-Detectivity and Low-Cost Short-Wave Infrared Photodetection: GeSn/Ge Multiple-Quantum-Well Photodetectors with a Dielectric Nanohole Array Metasurface.

High-detectivity and low-cost short-wave infrared photodetectors with complementary metal-oxide-semiconductor (CMOS) compatibility are attractive for various applications such as next-generation optical communication, LiDAR, and molecular sensing. Here, GeSn/Ge multiple-quantum-well (MQW) photodetectors with a dielectric nanohole array metasurface were proposed to realize high-detectivity and low-cost SWIR photodetection. The Ge nanohole array metasurface was utilized to enhance the light absorption in the GeSn/Ge MQW active layer. Compared with metallic nanostructures, the dielectric nanohole structure has the advantages of low intrinsic loss and CMOS compatibility. The introduction of metasurface architecture facilitates a 10.5 times enhanced responsivity of 0.232 A/W at 2 µm wavelength while slightly sacrificing the dark current density. Besides, the metasurface GeSn/Ge MQW photodetectors benefit 35% improvement in the 3 dB bandwidth compared to control GeSn/Ge MQW photodetectors, which can be attributed to the reduced RC delay. Due to the high responsivity and low dark current density, the room temperature specific detectivity at 2 µm is as high as 5.34 × 109 cm·Hz1/2/W, which is the highest among GeSn photodetectors and is better than commercial InSb and PbSe photodetectors operating at the similar wavelength. This work offers a promising approach for achieving low-cost and effective photodetection at 2 µm, contributing to the development of the 2 µm communication band.

Transferable single-layer GeSn nanomembrane resonant-cavity-enhanced photodetectors for 2 µm band optical communication and multi-spectral short-wave infrared sensing.

Semiconductor nanomembranes (NMs) have emerged as an attractive nanomaterial for advanced electronic and photonic devices with attractive features such as transferability and flexibility, enabling heterogeneous integration of multi-functional components. Here, we demonstrate transferable single-layer GeSn NM resonant-cavity-enhanced photodetectors for 2 µm optical communication and multi-spectral short-wave infrared sensing/imaging applications. The single-layer strain-free GeSn NMs with an Sn concentration of 10% are released from a high-quality GeSn-on-insulator (GSOI) substrate with the defective interface regions removed. By transferring the GeSn NMs onto a predesigned distribution Bragg reflector (DBR)/Si substrate, a vertical microcavity is integrated into the device to enhance the light-matter interaction in the GeSn NM. With the integrated cavity and high-quality single-layer GeSn NM, a record responsivity of 0.51 A W-1 at 2 µm wavelength at room temperature is obtained, which is more than two orders of magnitude higher than the reported values of the multiple-layer GeSn membrane photodetectors without cavities. The potential of the device for multi-spectral photodetection is demonstrated by tuning the responsivity spectrum with different NM thicknesses. Theoretical simulations are utilized to analyze and verify the mechanisms of responsivity enhancement. The approach can be applied to other GeSn-NM-based active devices, such as electro-absorption modulators or light emitters, presenting a new pathway towards heterogeneous group-IV photonic integrated circuits with miniaturized devices.

Real-world study of antiresorptive-related osteonecrosis of jaw based on the US food and drug administration adverse event reporting system database.

Objective: This study aims to explore the risk signals of osteonecrosis of the jaw induced by antiresorptive drugs and provide references for the clinical safety application. Method: According to the FDA's Adverse Event Reporting System (FAERS), from January 2004 to September 2021, we chose "Osteonecrosis of the jaw (10064658)" and "Exposed bone in jaw (10071014)" as preferred terms, "antiresorptive drugs" as the target drugs, and primary suspect drug as the drug role code in the dataset. We evaluated the association between drugs and adverse events by using reporting odds ratio (ROR) based on disproportionality analysis. We took the High-Level Terms (HLT) of MedDRA® as the classification level of indications to calculate ROR to compare the signal difference of ONJ in different indications. In addition, patients with antiresorptive-induced osteonecrosis of the jaw and the time of onset of the condition following different antiresorptive medications were collected for the study. Results: The FAERS contained 18,421 reports relating to jaw osteonecrosis from January 2004 to September 2021. A total of eight antiresorptive agents were included in the analysis. From high to low, the ROR of ONJ induced by antiresorptive agents (regardless of indication) is pamidronate (ROR = 494.8), zoledronic acid (ROR = 431.9), denosumab (ROR = 194.8), alendronate (ROR = 151.2), risedronate (ROR = 140.2), etidronic acid (ROR = 64.5), ibandronate (ROR = 40.8), and romosozumab (ROR = 6.4). HLT ROR values for "metabolic bone disorders" were the lowest for each drug, while HLT ROR values were high for "tumor-related indications," including breast and nipple neoplasms malignant, plasma cell myelomas, and prostatic neoplasms malignant. The onset time for osteonecrosis of the jaw as median (Q1, Q3), osteoporosis-related indications, and the onset time for ONJ were 730 (368, 1268), 489.5 (236.3, 909.8), 722.5 (314, 1055), 761 (368, 1720), and 153 (50, 346) for zoledronic acid, denosumab, ibandronate, risedronate, and romosozumab, respectively. Cancer-related indications: the onset time for ONJ were 680.5 (255.3, 1283), 488 (245, 851), and 696.5 (347, 1087) for zoledronic acid, denosumab, and pamidronate, respectively. Conclusion: When antiresorptive drugs are used for metastasis, they have the largest risk signal, followed by malignancy, and the smallest is osteoporosis. The onset time of ONJ may not be related to the indications. The onset time of ONJ for BPs was about 2 years, denosumab about 1.3 years, and romosozumab less than 1 year, which may be related to sequential treatment. When used according to the instructions, the risk of ONJ caused by denosumab was higher than that of zoledronic acid, regardless of the indication. Based on these findings, researchers will continue to monitor and identify risk factors.

Metal-Semiconductor-Metal GeSn Photodetectors on Silicon for Short-Wave Infrared Applications.

Metal-semiconductor-metal photodetectors (MSM PDs) are effective for monolithic integration with other optical components of the photonic circuits because of the planar fabrication technique. In this article, we present the design, growth, and characterization of GeSn MSM PDs that are suitable for photonic integrated circuits. The introduction of 4% Sn in the GeSn active region also reduces the direct bandgap and shows a redshift in the optical responsivity spectra, which can extend up to 1800 nm wavelength, which means it can cover the entire telecommunication bands. The spectral responsivity increases with an increase in bias voltage caused by the high electric field, which enhances the carrier generation rate and the carrier collection efficiency. Therefore, the GeSn MSM PDs can be a suitable device for a wide range of short-wave infrared (SWIR) applications.

InPBi Quantum Dots for Super-Luminescence Diodes.

InPBi thin film has shown ultra-broad room temperature photoluminescence, which is promising for applications in super-luminescent diodes (SLDs) but met problems with low light emission efficiency. In this paper, InPBi quantum dot (QD) is proposed to serve as the active material for future InPBi SLDs. The quantum confinement for carriers and reduced spatial size of QD structure can improve light emission efficiently. We employ finite element method to simulate strain distribution inside QDs and use the result as input for calculating electronic properties. We systematically investigate different transitions involving carriers on the band edges and the deep levels as a function of Bi composition and InPBi QD geometry embedded in InAlAs lattice matched to InP. A flat QD shape with a moderate Bi content of a few percent over 3.2% would provide the optimal performance of SLDs with a bright and wide spectrum at a short center wavelength, promising for future optical coherence tomography applications.

Theoretical Investigation of Biaxially Tensile-Strained Germanium Nanowires.

We theoretically investigate highly tensile-strained Ge nanowires laterally on GaSb. Finite element method has been used to simulate the residual elastic strain in the Ge nanowire. The total energy increment including strain energy, surface energy, and edge energy before and after Ge deposition is calculated in different situations. The result indicates that the Ge nanowire on GaSb is apt to grow along 〈100〉 rather than 〈110〉 in the two situations and prefers to be exposed by {105} facets when deposited a small amount of Ge but to be exposed by {110} when the amount of Ge exceeds a critical value. Furthermore, the conduction band minima in Γ-valley at any position in both situations exhibits lower values than those in L-valley, leading to direct bandgap transition in Ge nanowire. For the valence band, the light hole band maxima at Γ-point is higher than the heavy hole band maxima at any position and even higher than the conduction band minima for the hydrostatic strain more than ∼5.0%, leading to a negative bandgap. In addition, both electron and hole mobility can be enhanced by owing to the decrease of the effective mass under highly tensile strain. The results suggest that biaxially tensile-strained Ge nanowires hold promising properties in device applications.

Detailed Study of the Influence of InGaAs Matrix on the Strain Reduction in the InAs Dot-In-Well Structure.

InAs/InGaAs dot-in-well (DWELL) structures have been investigated with the systematically varied InGaAs thickness. Both the strained buffer layer (SBL) below the dot layer and the strain-reducing layer (SRL) above the dot layer were found to be responsible for the redshift in photoluminescence (PL) emission of the InAs/InGaAs DWELL structure. A linear followed by a saturation behavior of the emission redshift was observed as a function of the SBL and SRL thickness, respectively. The PL intensity is greatly enhanced by applying both of the SRL and SBL. Finite element analysis simulation and transmission electron microscopy (TEM) measurement were carried out to analyze the strain distribution in the InAs QD and the InGaAs SBL. The results clearly indicate the strain reduction in the QD induced by the SBL, which are likely the main cause for the emission redshift.

A new route toward light emission from Ge: tensile-strained quantum dots.

The tensile-strained Ge quantum dot (QD) is proposed as a new route for the realization of direct band gap conversion in Ge. Ge QDs were successfully grown on an InP substrate by molecular beam epitaxy. The strain field in the QDs were analyzed by high resolution transmission electron microscopy and simulated by the finite element method based on the measured geometries. The strain field in the QDs is found to be non-uniform and the shear component plays a significant role in the energy band structure, leading to larger required hydrostatic strain than that in the Ge thin films under biaxial strain to become a direct band gap.