Room Temperature InP DFB Laser Array Directly Grown on (001) Silicon

Fully exploiting the silicon photonics platform requires a fundamentally new approach to realize high-performance laser sources that can be integrated directly using wafer-scale fabrication methods. Direct band gap III-V semiconductors allow efficient light generation but the large mismatch in lattice constant, thermal expansion and crystal polarity makes their epitaxial growth directly on silicon extremely complex. Here, using a selective area growth technique in confined regions, we surpass this fundamental limit and demonstrate an optically pumped InP-based distributed feedback (DFB) laser array grown on (001)-Silicon operating at room temperature and suitable for wavelength-division-multiplexing applications. The novel epitaxial technology suppresses threading dislocations and anti-phase boundaries to a less than 20nm thick layer not affecting the device performance. Using an in-plane laser cavity defined by standard top-down lithographic patterning together with a high yield and high uniformity provides scalability and a straightforward path towards cost-effective co-integration with photonic circuits and III-V FINFET logic

Heterogeneous integration on silicon photonics

To enhance the functionality of the standard silicon photonics platform and to overcome its limitations, in particular for light emission, ultrafast modulation, and nonlinear applications, integration with novel materials is being investigated by several groups. In this paper, we will discuss, among others, the integration of silicon waveguides with ferroelectric materials such as lead zirconate titanate (PZT) and barium titanate (BTO), with electro-optically active polymers, with 2-D materials such as graphene and with III-V semiconductors through epitaxy. We discuss both the technology and design aspects

III-V-on-silicon photonic devices for optical communication and sensing

In the paper, we review our work on heterogeneous III-V-on-silicon photonic components and circuits for applications in optical communication and sensing. We elaborate on the integration strategy and describe a broad range of devices realized on this platform covering a wavelength range from 850 nm to 3.85 μm

High-Performance Quantum Dot Lasers and Integrated Guided-Wave Devices on Silicon.

Optical interconnects, the chip-scale integration of optoelectronic devices with complementary-metal-oxide-semiconductor (CMOS) silicon circuits, provide a promising approach for the realization of the next-generation high-speed computing and communication systems. Unfortunately, optoelectronics lacks an obvious platform for monolithic integration. One of the practical solutions is the hybrid integration, through heteroepitaxial growth, of compound semiconductor optoelectronic components with silicon technology. This thesis is devoted to developing high-performance GaAs-based quantum dot lasers directly grown on silicon substrates and their monolithic integration with waveguides and electroabsorption modulators. The investigation of 1.5 μm siliconbased high-Q random photonic crystal microcavity light emitters utilizing PbSe colloidal quantum dots has also been conducted. High-performance quantum dot lasers directly-grown on silicon substrates have been achieved in this study. The performance of III-V-based lasers on silicon can be degraded by the inherent high-density propagating dislocations. To enhance device performance, a novel quantum dot dislocation filter has been developed. The best lasers exhibit relatively low threshold current density (Jth = 900 A/cm2), large small-signal modulation bandwidth of 5.5 GHz, and a high characteristic temperature (T0 = 278 K). The monolithic integration of InGaAs QD lasers with waveguides and quantum well(QW) electroabsorption modulators has been achieved through molecular beam epitaxy (MBE) growth and regrowth. Focused-ion-beam milling is utilized to create high-quality etched GaAs facets with a reflectivity of 0.28 and coupling groove with coupling coefficient greater than 20%. Quantum-dot lasers with focused-ion-beam-etched facets exhibit comparable performance to those with cleaved facets. The integrated modulator exhibits a modulation depth ~100% at 5 V reverse bias. In addition, the monolithic integration of the amorphous silicon waveguide with quantum dot laser has also been demonstrated by using plasma-enhanced-chemical-vapor deposition (PECVD). Finally, enhanced photoluminescence at 1.5 μm wavelength has been observed from PbSe colloidal quantum dots embedded in a silicon-based random photonic crystal microcavity. Such microscale light sources on silicon can also be fabricated or integrated on silicon CMOS chips, which may provide a viable route for inter- and intrachip optical communications.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/60821/1/junyang_1.pd

III-Nitride Self-assembled Nanowire Light Emitting Diodes and Lasers on (001) Silicon.

Substantial research is being devoted to the development of III-nitride light emitting diodes (LEDs) and lasers, which have numerous applications in solid state lighting. In particular, white LEDs play an increasingly important role in our daily lives. Current commercially available white LEDs are nearly all phosphor-converted, but these have some serious disadvantages. Planar quantum well (QW) devices on foreign substrates exhibit large threading dislocation densities, strong strain induced polarization field, and In-rich nanoclusters resulting in poor electron-hole wavefunction overlap, large emission peak shift with injection, and large efficiency drop at high injection currents in LEDs and large threshold current densities in lasers. The objective of this doctoral research is to investigate the prospects of self-assembled InGaN/GaN disks-in-nanowire (DNW) LEDs and lasers for solid state lighting. The research described here embodies a detailed study of the optical and structural characteristics of the nanowire heterostructures by varying the growth conditions and by surface passivation, and using the disks as the active region in high performance nanowire LEDs and gain medium in nanowire lasers on (001) silicon. Self-assembled InGaN/GaN DNWs are grown in a plasma-assisted molecular beam epitaxy (PA-MBE) system. Due to their large surface to volume ratio, the growth optimized and surface passivated DNWs on (001) silicon are relatively free of extended defects and have smaller polarization field resulting in higher radiative efficiencies. Blue-, green- and red-emitting DNW LEDs, with optimized nanowire densities, are demonstrated with reduced efficiency droop and smaller peak shift with injection. Phosphor-free white nanowire LEDs are realized by incorporating InGaN/GaN disks with different color emissions in the active region. The first ever monolithic edge-emitting electrically pumped green and red nanowire lasers on (001) silicon are demonstrated using DNWs as the gain media and are characterized by low threshold current densities of 1.76-2.88 kA/cm2, small peak shifts of 11-14.8 nm, large T0 of 234 K and large differential gain of 3x10-17 cm-2. Dynamic measurements performed on these lasers yield a maximum small signal modulation bandwidth of 5.8 GHz, extremely low value of chirp (0.8 Å) and a near-zero linewidth enhancement factor at the peak emission wavelength.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111490/1/shafat_1.pd

CMOS Integration of High Performance Quantum Dot Lasers For Silicon Photonics

Integration of III-V components on Si substrates is required for realizing the promise of Silicon Photonic systems. Specifically, the direct bandgap of many III-V materials is required for light sources, efficient modulators and photodetectors. Several different approaches have been taken to integrate III-V lasers into the silicon photonic platform, such as wafer bonding, direct growth, butt coupling, etc. Here, we have devised a novel laser design that overcomes the above limitations. In our approach, we use InAs quantum dot (QD) lasers monolithically integrated with silicon waveguides and other Si photonic passive components. Due to their unique structures, the QD lasers have been proven by several groups to have the combination of high temperature stability, large modulation bandwidth and low power consumption compared with their quantum well counterparts, which makes it an ideal candidate for Si photonic applications. The first section of this dissertation introduces the theory and novelty of QD lasers, the DC and RF characterization methods of QD lasers are also discussed. The second section is focused on the growth of QD gain chip which a broadband gain chip based on QD inhomogeneous broadening properties was demonstrated. In third section, the lasers devices are built on Si substrate by Pd wafer bonding technology. Firstly, a ridge waveguide QD laser is demonstrated in this section which have better heat dissipation and lower threshold current compared to the unbonded lasers. In section four, a on Si comb laser is also developed. Due to inhomogeneous broadening and ultrafast carrier dynamics, InAs quantum dots have key advantages that make them well suited for Mode-locked lasers (MLLs). In section five, a passively mode-locked InAs quantum dots laser on Si is achieved at a repetition rate of ~7.3 GHz under appropriate bias conditions. In section six, a butt-joint integration configuration based on QD lasers and silicon photonics ring resonator is tested by using to translation stage. In order to achieve the on chip butt-joint integration, an on chip laser facet was created in section seven. A novel facet etching method is developed by using Br-ion beam assist etching (Br-IBAE). In section eight, a Pd-GaAs butt-joint integration platform was proposed, a hybrid tunable QD laser which consist of a QD SOA gain chip butt joint coupled with a passive Si3N4 photonic integrated circuit is proof of concept by using an external booster SOA coupled with a Si3N4 ring reflector feedback circuit. The final section summarized the work discussed in this thesis and also discussed some future approaches by using QD lasers integrated with silicon photonics integrated circuits based on the Pd-GaAs wafer bonding butt-joint coupled platform

Growth, processing, and optical properties of epitaxial Er_2O_3 on silicon

Erbium-doped materials have been investigated for generating and amplifying light in low-power chip-scale optical networks on silicon, but several effects limit their performance in dense microphotonic applications. Stoichiometric ionic crystals are a potential alternative that achieve an Er^(3+) density 100× greater. We report the growth, processing, material characterization, and optical properties of single-crystal Er_2O_3 epitaxially grown on silicon. A peak Er^(3+) resonant absorption of 364 dB/cm at 1535nm with minimal background loss places a high limit on potential gain. Using high-quality microdisk resonators, we conduct thorough C/L-band radiative efficiency and lifetime measurements and observe strong upconverted luminescence near 550 and 670 nm

GaAs nano-ridge laser diodes fully fabricated in a 300 mm CMOS pilot line

Silicon photonics is a rapidly developing technology that promises to revolutionize the way we communicate, compute, and sense the world. However, the lack of highly scalable, native CMOS-integrated light sources is one of the main factors hampering its widespread adoption. Despite significant progress in hybrid and heterogeneous integration of III-V light sources on silicon, monolithic integration by direct epitaxial growth of III-V materials remains the pinnacle in realizing cost-effective on-chip light sources. Here, we report the first electrically driven GaAs-based multi-quantum-well laser diodes fully fabricated on 300 mm Si wafers in a CMOS pilot manufacturing line. GaAs nano-ridge waveguides with embedded p-i-n diodes, InGaAs quantum wells and InGaP passivation layers are grown with high quality at wafer scale, leveraging selective-area epitaxy with aspect-ratio trapping. After III-V facet patterning and standard CMOS contact metallization, room-temperature continuous-wave lasing is demonstrated at wavelengths around 1020 nm in more than three hundred devices across a wafer, with threshold currents as low as 5 mA, output powers beyond 1 mW, laser linewidths down to 46 MHz, and laser operation up to 55 {\deg}C. These results illustrate the potential of the III-V/Si nano-ridge engineering concept for the monolithic integration of laser diodes in a Si photonics platform, enabling future cost-sensitive high-volume applications in optical sensing, interconnects and beyond.Comment: 40 pages with 16 figures. pdf includes supplementary informatio

Colloidal quantum dots enabling coherent light sources for integrated silicon-nitride photonics

Integrated photoniccircuits, increasingly based on silicon (-nitride), are at the core of the next generation of low-cost, energy efficient optical devices ranging from on-chip interconnects to biosensors. One of the main bottlenecks in developing such components is that of implementing sufficient functionalities on the often passive backbone, such as light emission and amplification. A possible route is that of hybridization where a new material is combined with the existing framework to provide a desired functionality. Here, we present a detailed design flow for the hybridization of silicon nitride-based integrated photonic circuits with so-called colloidal quantum dots (QDs). QDs are nanometer sized pieces of semiconductor crystals obtained in a colloidal dispersion which are able to absorb, emit, and amplify light in a wide spectral region. Moreover, theycombine cost-effective solution based deposition methods, ambient stability, and low fabrication cost. Starting from the linear and nonlinear material properties obtained on the starting colloidal dispersions, we can predict and evaluate thin film and device performance, which we demonstrate through characterization of the first on-chip QD-based laser