Quantum dot lasers and integrated optoelectronics on silicon platform Invited Paper

Chip-scale integration of optoelectronic devices such as lasers, waveguides, and modulators on silicon is prevailing as a promising approach to realize future ultrahigh speed optical interconnects. We review recent progress of the direct epitaxy and fabrication of quantum dot （QD） lasers and integrated guided-wave devices on silicon. This approach involves the development of molecular beam epitaxial growth of self- organized QD lasers directly on silicon substrates and their monolithic integration with amorphous silicon waveguides and quantum well electroabsorption modulators. Additionally, we report a preliminary study of long-wavelength （〉 1.3 μm） QD lasers grown on silicon and integrated crystalline silicon waveguides using membrane transfer technology.

Integrated optoelectronics with two-dimensional materials

As we enter the post-Moore era,heterogeneous optoelectronic integrated circuits(OEICs)are attracting significant attention as an alternative approach to scaling to smaller-sized transistors.Two-dimensional(2D)materials,offering a range of intriguing optoelectronic properties as semiconductors,semimetals,and insulators,provide great potential for developing nextgeneration heterogeneous OEICs.For instance,Fermi levels of 2D materials can be tuned by applying electrical voltages,while their atomically thin geometries are inherently suited for the fabrication of planar devices without suffering from lattice mismatch.Since the first graphene-on-silicon OEICs were demonstrated in 2011,2D-material heterogeneous OEICs have significantly progressed.To date,researchers have a better understanding of the importance of interface states on the optical properties of chip-integrated 2D materials.Moreover,there has been impressive progress towards the use of 2D materials for waveguide-integrated lasers,modulators,and photodetectors.In this review,we summarize the history,status,and trend of integrated optoelectronics with 2D materials.

Monolithically Integrated Laser Diode and Electroabsorption Modulator with Dual-Waveguide Spot-Size Converter Output

A 1.60μm laser diode and electroabsorption modulator monolithically integrated with a novel dual-waveguide spot-size converter output for low-loss coupling to a cleaved single-mode optical fiber are demonstrated.The devices emit in a single transverse and quasi single longitudinal mode with an SMSR of 25.6dB.These devices exhibit a 3dB modulation bandwidth of 15.0GHz,and modulator DC extinction ratios of 16.2dB.The output beam divergence angles of the spot-size converter in the horizontal and vertical directions are as small as 7.3°×18.0°,respectively,resulting in a 3.0dB coupling loss with a cleaved single-mode optical fiber.

1.55μm Laser Diode Monolithically Integrated with Spot-Size Converter Using Conventional Process

A novel 1 55μm laser diode with spot size converter is designed and fabricated using conventional photolithography and chemical wet etching process.For the laser diode,a ridge double core structure is employed.For the spot size converter,a buried ridge double core structure is incorporated.The laterally tapered active core is designed and optically combined with the thin and wide passive core to control the size of mode.The laser diode threshold current is measured to be 40mA together with high slop efficiency of 0 35W/A.The beam divergence angles in the horizontal and vertical directions are as small as 14 89°×18 18°,respectively,resulting in low coupling losses with a cleaved optical fiber (3dB loss).

Design and Implementation of an Optoelectronic Integrated Receiver in Standard CMOS Process

A wideband monolithic optoelectronic integrated receiver with a high-speed photo-detector,completely compatible with standard CMOS processes,is designed and implemented in 0.6μm standard CMOS technology.The experimental results demonstrate that its performance approaches applicable requirements,where the photo-detector achieves a -3dB frequency of 1.11GHz,and the receiver achieves a 3dB bandwidth of 733MHz and a sensitivity of -9dBm for λ=850nm at BER=10-12.

Integrated model optocouplers

Utilizing hybrid integration model.the integrated model optocouplers have successfully developed.The design,fabrication and characteristic parameters of the devices are presented.

Butt-Joint Monolithically Integrated DFB-LD/EA-MD Light Source for 10Gbit/s Transmission

This paper reports on the design,fabrication,and performance of an integrated electro-absorptive modulated laser based on butt-joint configuration for 10Gbit/s application.This paper mainly aims at two aspects.One is to improve the optical coupling between the laser and modulator;another is to increase the bandwidth of such devices by reducing the capacitance parameter of the modulator.The integrated devices exhibit high static and dynamic characteristics. Typical threshold current is 15mA,with some value as low as 8mA.Output power at 100mA is more than 10mW.The extinction characteristics,modulation bandwidth,and electrical return loss are measured.3dB bandwidth more than 10GHz is monitored.

Enhancement of electroluminescent properties of organic optoelectronic integrated device by doping phosphorescent dye

Organic optoelectronic integrated devices（OIDs） with ultraviolet（UV） photodetectivity and different color emitting were constructed by using a thermally activated delayed fluorescence（TADF） material 4, 5-bis（carbazol-9-yl）-1, 2-dicyanobenzene（2 CzPN） as host. The OIDs doping with typical red phosphorescent dye [tris（1-phenylisoquinoline）iridium（Ⅲ）, Ir（piq）3], orange phosphorescent dye {bis[2-（4-tertbutylphenyl）benzothiazolato-N,C-（2＇）]iridium（acetylacetonate）,（tbt）2 Ir（acac）}, and blue phosphorescent dye [bis（2, 4-di-fluorophenylpyridinato）-tetrakis（1-pyrazolyl）borate iridium（Ⅲ）, FIr6] were investigated and compared. The（tbt）2 Ir（acac）-doped orange device showed better performance than those of red and blue devices, which was ascribed to more effective energy transfer. Meanwhile, at a low dopant concentration of 3 wt.%, the（tbt）2 Ir（acac）-doped OIDs showed the maximum luminance, current efficiency, power efficiency of 70786 cd/m^2, 39.55 cd/A, and 23.92 lm/W, respectively, and a decent detectivity of 1.07 × 10^11 Jones at a bias of -2 V under the UV-350 nm illumination. This work may arouse widespread interest in constructing high efficiency and luminance OIDs based on doping phosphorescent dye.

16-Channel 0.35μm CMOS/VCSEL Transmission Modules

The vertical cavity surface emitting laser (VCSEL) arrays and VCSEL-based optical transmission modules are investigated.It includes the VCSEL's spectral characteristic,modulation characteristic,high frequency characteristic,and compatibility with microelectronic circuit.The module consists of 1×16 VCSEL array and 16-channel lasers driver with 0.35μm CMOS circuit by hybrid integration.During the test process,the module operates well at more than 2GHz in -3dB frequency bandwidth.

A 1.25Gb/s InP-Based Vertical Monolithic Integration of an MQW Laser Diode and an HBT Driver witha Lateral Buffer Mes a Structure

A novel fabrication process related to a smoothly wet chemical etching profile o f InP-based epitaxial layers in the crystal direction of [01for an InP-based monol ithic vertically integrated transmitter with an MQW laser diode and a heterojunction bipolar tran sistors driver circuit is described.A clear eye output diagram via an O/E converter is demonstrat ed und er a 1.25Gb/s non-return-zero pseudorandom code with a pattern length of 2 the integrated transmitter has a power dissipation of about 120mW with an optical output of 2dBm.

A High-Performance Silicon Electro-Optic Phase Modulator with a Triple MOS Capacitor

We propose and analyze a novel Si-based electro-optic modulator with an improved metal-oxide-semiconductor （MOS） capacitor configuration integrated into silicon-on-insulator （SOl）. Three gate-oxide layers embedded in the silicon waveguide constitute a triple MOS capacitor structure, which boosts the modulation efficiency compared with a single MOS capacitor. The simulation results demonstrate that the Vπ Lπ product is 2. 4V · cm. The rise time and fall time of the proposed device are calculated to be 80 and 40ps from the transient response curve, respectively,indicating a bandwidth of 8GHz. The phase shift efficiency and bandwidth can be enhanced by rib width scaling.

Bandwidth Design for CMOS Monolithic Photoreceiver

A monolithic photoreceiver which consists of a double photodiode (DPD) detector and a regulated cascade (RGC) transimpedance amplifier (TIA) is designed.The small signal circuit model of DPD is given and the bandwidth design method of a monolithic photoreceiver is presented.An important factor which limits the bandwidth of DPD detector and the photoreceiver is presented and analyzed in detail.A monolithic photoreceiver with 1.71GHz bandwidth and 49dB transimpedance gain is designed and simulated by applying a low-cost 0.6μm CMOS process and the test result is given.

Zero-bias high-responsivity high-bandwidth top-illuminated germanium p–i–n photodetectors

We report efficient zero-bias high-speed top-illuminated p-i-n photodiodes （PDs） with high responsivity fabricated with germanium （Ge） films grown directly on silicon-on-insulator （SOI） substrates. For a 15 p-m-diameter device at room temperature, the dark current density was 44.1 mA/cm2 at -1 V. The responsivity at 1.55 μm was 0.30 A/W at 0 V. The saturation of the optical responsivity at 0 V bias revealed that this photodetector allows a complete photo-generated carrier collection without bias. Although the 3-dB bandwidth of the 15-p.m-diameter detector was 18.8 GHz at the reverse bias of 0 V, the detector responsivity was improved by one order of magnitude compared with that reported in the literature. Moreover, the dark current of the detector was significantly reduced.

Monolithically Fabricated OEICs Using RTD and MSM

Two kinds of monolithically fabricated circuits are demonstrated in GaAs-based material systems using resonant tunneling diodes（RTD） and metal-semiconductor-metal photo detectors（MSM PD）. The electronic characteristics of these fabricated RTD devices,MSM devices,and integrated circuits are tested at room temperature. The results show that the current peak-to-valley ratio is 4,and the photocurrent at 5V is enhanced by a factor of nearly 9,from 2 to about 18μA by use of recessed electrodes. The working theory and logical functions of the circuits are validated.

Multifunctional silicon-based light emitting device in standard complementary metal oxide semiconductor technology

A three-terminal silicon-based light emitting device is proposed and fabricated in standard 0.35 μm complementary metal-oxide-semiconductor technology. This device is capable of versatile working modes： it can emit visible to near infra-red （NIR） light （the spectrum ranges from 500 nm to 1000 nm） in reverse bias avalanche breakdown mode with working voltage between 8.35 V-12 V and emit NIR light （the spectrum ranges from 900 nm to 1300 nm） in the forward injection mode with working voltage below 2 V. An apparent modulation effect on the light intensity from the polysilicon gate is observed in the forward injection mode. Furthermore, when the gate oxide is broken down, NIR light is emitted from the polysilicon/oxide/silicon structure. Optoelectronic characteristics of the device working in different modes are measured and compared. The mechanisms behind these different emissions are explored.

Design of a 12-Gbit/s CMOS DNFFCG differential transimpedance amplifier

A 12-Gbit/s low-power,wide-bandwidh CMOS(complementary metal oxide semiconductor)dual negative feedback feed-forward common gate(DNFFCG)differential trans-impedance amplifier(TIA)is presented for the veryshort-reach(VSR)optoelectronic integrated circuit(OEIC)receiver.The dominant pole of the input node is shifted up to a high frequency,and thus the bandwidth of the CMOS DNFFCG TIA is improved.Besides,two negative feedback loops are used to reduce the input impedance and further increase the bandwidth.The proposed TIA was fabricated using TSMC 0.18 jxm CMOS technology.The whole circuit has a compact chip area,the core area of which is only 0.003 6 mm2.The power consumption is 14.6 mW excluding 2-stage differential buffers.The test results indicate that the 3 dB bandwidth of 9 GHz is achieved with a 1 8 V supply voltage and its trans-impedance gain is 49.2 dBH.The measured average equivalent input noise current density is 28.1 pA H z12.Under the same process conditions,the DNFFCG has better gain bandwidth product compared with those in the published papers.

Simulating Experiment and Circuit Simulation of RTD/HPT Photo-Controlled MOBILE

The MOBILE is a logic element realizing the monostable-bistable transition of a circuit that consists of two resonant tunneling transistors—the resonant tunneling diodes (RTDs) connected in series. It has several advantages including multiple inputs and multiple functions. In this paper, by connecting a heterojunction phototransistor (HPT) with the MOBILE, a novel optoelectronic functional device can be got, which presents the function of both photocurrent switching and photocurrent latching. These behaviors have been demonstrated for the first time by simulating experiments and circuit simulations, with RTDs firstly manufactured in China. Research indicates that the novel photo-controlled MOBILE has the same logic functions as conventional electrical MOBILE except for with light as an input signal.

Progress of Si-based Optoelectronic Devices

Si-based optoelectronics is becoming a very active research area due to its potential applications to optical communications.One of the major goals of this study is to realize all-Si optoelectronic integrated circuit.This is due to the fact that Si-based optoelectronic technology can be compatible with Si microelectronic technology.If Si-based optoelectronic devices and integrated circuits can be achieved,it will lead to a new informational technological revolution.In the article,the current developments of this exciting field are mainly reviewed in the recent years.The involved contents are the realization of various Si-based optoelectronic devices,such as light-emitting diodes,optical waveguides devices,Si photonic bandgap crystals,and Si laser,etc.Finally,the developed tendency of all-Si optoelectronic integrated technology are predicted in the near future.

Efficient evanescent coupling design for GeSi electro-absorption modulator

Efficient coupling from the silicon waveguide to the GeSi layer is the key to success in the GeSi electro-absorption （EA） modulator based on evanescent coupling. A lateral taper in the upper GeSi layer has room for increasing the modulating efficiency and alleviating the sensitivity of the extinction ratio （ER） and insertion loss （IL） to the length of the active region. The light behavior and the effect of the taper are explored in detail using the beam propagation method （BPM）. After optimization, the light can nearly be totally confined in the GeSi layer without any oscillation. The modulator with the designed taper can achieve low IL and high ER.

Progress in complementary metal–oxide–semiconductor silicon photonics and optoelectronic integrated circuits

Silicon photonics is an emerging competitive solution for next-generation scalable data communications in different application areas as high-speed data communication is constrained by electrical interconnects. Optical interconnects based on silicon photonics can be used in intra/inter-chip interconnects, board-to-board interconnects, short-reach communications in datacenters, supercomputers and long-haul optical transmissions. In this paper, we present an overview of recent progress in silicon optoelectronic devices and optoelectronic integrated circuits （OEICs） based on a complementary metal-oxide-semiconductor-compatible process, and focus on our research contributions. The silicon optoelectronic devices and OEICs show good characteristics, which are expected to benefit several application domains, including communication, sensing, computing and nonlinear systems.