High performance silicon-based GeSn p–i–n photodetectors for short-wave infrared application

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.

Enhanced Current Transportation in Siliconriched Nitride(SRN)/Silicon-riched Oxide(SRO)Multilayer Nanostructure

A novel structure of silicon-riched nitride(SRN)/silicon-riched oxide(SRO) is proposed and prepared using RF reactive magnetron co-sputtering. High temperature annealing of SRN/SRO multilayers leads to formation of Si nanocrystals(NC) from isolating SRN and SRO layers simultaneously, which efficiently improves carrier transport ability compared to conventional SRN/Si_3N_4 counterpart. Micro-Raman scattering analysis reveals that SRN layer has dominating number of denser and smaller Si NCs, while SRO layer has relatively less, sparser and bigger Si NCs, as confirmed by high resolution transmission electron microscopy observation. The substitute SRO layers for Si_3N_4 counterparts significantly increase the amount of Si NCs as well as crystallization ratio in SRN layers; while the average Si NC size can be well controlled by the thickness of SRN layers and the content of N, and hence an obvious stronger absorption in UV region for the novel structure can be observed in absorption spectra. The I-V characteristics show that the current of hybrid SRN/SRO system increases up to 2 orders of magnitude at 1 V and even 5 orders of magnitude at 4 V compared to that of SRN/Si_3N_4 structure. Si NCs in Si Oylayers provide a transport pathway for adjacent Si NCs in Si Nxlayers. The obvious advantage in carrier transportation suggests that SRN/SRO hybrid system could be a promising structure and platform to build Si nanostructured solar cells.

Germanium/perovskite heterostructure for high-performance and broadband photodetector from visible to infrared telecommunication band

A high-performance and broadband heterojunction photodetector has been successfully fabricated.The heterostructure device is based on a uniform and pinhole-free perovskite film constructed on top of a single-crystal germanium layer.The perovskite/germanium photodetector shows enhanced performance and a broad spectrum compared with the single-material-based device.The photon response properties are characterized in detail from the visible to near-infrared spectrum.At an optical fibre communication wavelength of 1550 nm,the heterojunction device exhibits the highest responsivity of 1.4 A/W.The performance is promoted because of an antireflection perovskite coating,the thickness of which is optimized to 150 nm at the telecommunication band.At a visible light wavelength of 680 nm,the device shows outstanding responsivity and detectivity of 228 A/W and 1.6×10^(10) Jones,respectively.These excellent properties arise from the photoconductive gain boost in the heterostructure device.The presented heterojunction photodetector provides a competitive approach for wide-spectrum photodetection from visible to optical communication areas.Based on the distinguished capacity of light detection and harvesting from the visible to near-infrared spectrum,the designed germanium/perovskite heterostructure configuration is believed to provide new building blocks for novel optoelectronic devices.

30 GHz GeSn photodetector on SOI substrate for 2 µm wavelength application

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.

25 × 50 Gbps wavelength division multiplexing silicon photonics receiver chip based on a silicon nanowire-arrayed waveguide grating

A high-performance monolithic integrated wavelength division multiplexing silicon(Si) photonics receiver chip is fabricated on a silicon-on-insulator platform. The receiver chip has a 25-channel Si nanowire-arrayed waveguide grating, and each channel is integrated with a high-speed waveguide Ge-on-Si photodetector. The central wavelength, optical insertion loss, and cross talk of the array waveguide grating are 1550.6 nm, 5–8 dB, and-12 –-15 dB, respectively. The photodetectors show low dark current density of 16.9 mA∕cm^2 at-1 V and a high responsivity of 0.82 A/W at 1550 nm. High bandwidths of 23 and 29 GHz are achieved at 0 and-1 V, respectively. Each channel can operate at 50 Gbps with low input optical power even under zero bias,which realizes an aggregate data rate of 1.25 Tbps.

Horizontal GeSn/Ge multi-quantum-well ridge waveguide LEDs on silicon substrates

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.

Recent progress in GeSn growth and GeSn-based photonic devices

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.

56 Gbps high-speed Ge electro-absorption modulator

A high-speed evanescent-coupled Ge waveguide electro-absorption modulator(EAM)with simple fabrication processes was realized on a silicon-on-insulator platform with a 220 nm top Si layer.Selectively grown Ge with a triangle shape was directly used for Ge waveguides of the EAM.An asymmetric p-i-n junction was designed in the Ge waveguide to provide a strong electric field for Franz-Keldysh effect.The insertion loss of the Ge EAM was 6.2 dB at 1610 nm.The EAM showed the high electro-optic bandwidth of 36 GHz at-1 V.Clear open 56 Gbps eye diagrams were observed at 1610 nm with a dynamic extinction ratio of 2.7 dB and dynamic power consumption of 45 fJ/bit for voltage swing of 3Vpp.

Ge-on-Si for Si-based integrated materials and photonic devices

This paper reviews the recent progress in photonic devices application of Ge-on-Si. Ge-on-Si materials and optical devices are suitable candidates for Si-based optoelectronic integration because of the mature epitaxial technique and the compatibility with Si complementary metal-oxide-semiconductor （CMOS） technology. Recently, the realities of electric-pump Ge light emitting diode （LED） and optical-pump pulse Ge laser, Ge quantum well modulator based on quantum Stark confined effect, waveguide Ge modulator based on Franz-Keldysh （FK） effect, and high performance near-infrared Ge detector, rendered the Si-based optoelectronic integration using Ge photonic devices. Ge-on-Si material is also an important platform to grow other materials on it for Si- based optoelectronic integration. InGaAs and GeSn have been grown on the Ge-on-Si. InGaAs LED and GeSn photodetector have been successfully fabricated as well.

Effect of the silicon substrate structure on chip spiral inductor

In this paper,the effect of the substrate structure on the performance of the spiral inductor is investigated by the 3-D electromagnetic simulator,Ansoft high frequency structure simulator(HFSS).With variations in the substrate structure including substrate conductivity,permittivity and thickness of the dielectric layer,the performance of the inductors has been analyzed in detail.The simulation results and analyses indicate that the performance of the spiral inductor can be mostly improved by lowering the conductivity of the substrate,increasing the thickness of the dielectric layer and using the low K dielectric layer.In the mean time,some guidelines or“design rules”are summarized by the results of this study.

High gain-bandwidth product Ge/Si tunneling avalanche photodiode with high-frequency tunneling effect

This study presents a theoretical investigation of a novel Ge/Si tunneling avalanche photodiode（TAPD）with an ultra-thin barrier layer between the absorption and p＋ contact layer. A high-frequency tunneling effect is introduced into the structure of the barrier layer to increase the high-frequency response when frequency is larger than 0.1 GHz, and the-3 dB bandwidth of the device increases evidently. The results demonstrate that the avalanche gain and-3 dB bandwidth of the TAPD can be influenced by the thickness and bandgap of the barrier layer.When the barrier thickness is 2 nm and the bandgap is 4.5 eV, the avalanche gain loss is negligible and the gainbandwidth product of the TAPD is 286 GHz, which is 18% higher than that of an avalanche photodiode without a barrier layer. The total noise in the TAPD was an order of magnitude smaller than that in APD without barrier layer.

Research progress of Ge on insulator grown by rapid melting growth

Ge is an attractive material for Si-based microelectronics and photonics due to its high carries mobility, pseudo direct bandgap structure, and the compatibility with complementary metal oxide semiconductor （CMOS） processes. Based on Ge, Ge on insulator （GOI） not only has these advantages, but also provides strong electronic and optical confinement. Recently, a novel technique to fabricate GOI by rapid melting growth （RMG） has been described. Here, we introduce the RMG technique and review recent efforts and progress in RMG. Firstly, we will introduce process steps of RMG. We will then review the researches which focus on characterizations of the GOI including growth dimension, growth mechanism, growth orientation, concentration distribution, and strain status. Finally, GOI based applications including high performance metal-oxide-semiconductor field effect transistors （MOSFETs） and photodetectors will be discussed. These results show that RMG is a promising technique for growth of high quality GOIs with different characterizations. The GOI grown by RMG is a potential material for the next-generation of integrated circuits and optoelectronic circuits.