Search

Gallium Phosphide (GaP) has recently received considerable attention as a suitable material for building photonic integrated circuits due to its remarkable optical and piezoelectric properties. Usually, GaP is grown epitaxially on III–V substrates to keep its crystallinity and later transferred to silicon wafers for further processing. Here, an alternative promising route for the fabrication of optomechanical (OM) cavities on GaP epitaxially grown on nominally (001)‐oriented Si is introduced by using a two‐step process consisting of a low‐temperature etching of GaP followed by selective etching of the underneath silicon. The low‐temperature (–30 °C) during the dry‐etching of GaP hinders the lateral etching rate, preserving the pattern with a deviation between the design and the pattern in the GaP layer lower than 5%, avoiding the complex process of transferring and bonding a GaP wafer to a silicon‐on‐insulator wafer. To demonstrate the quality and feasibility of the proposed fabrication route, suspended OM cavities are fabricated and experimentally characterized. The cavities exhibit optical quality factors between 103 and 104 at telecom wavelengths, and localized mechanical resonances ≈3.1 GHz with quality factors ≈63 when measured at room temperature. These results suggest a simple and low‐cost way to build GaP‐based photonic devices directly integrated on industry‐standard Si(001) photonic wafers. [ABSTRACT FROM AUTHOR]

An integrated optical isolator is a crucial part of photonic integrated circuits (PICs). Existing optical isolators, predominantly based on the silicon-on-insulator (SOI) platform, face challenges in integrating with active devices. We propose a broadband, compact TM mode Mach–Zehnder optical isolator based on InP-on-insulator platforms. We designed two distinct magneto-optical waveguide structures, employing different methods for bonding Ce:YIG and InP, namely O2 plasma surface activation direct wafer bonding and DVS-benzocyclobutene (BCB) adhesive bonding. Detailed calculations and optimizations were conducted to enhance their non-reciprocal phase shift (NRPS). At a wavelength of 1550 nm, the direct-bonded waveguide structure achieved a 30 dB bandwidth of 72 nm with a length difference of 0.256 µm. The effects of waveguide arm length, fabrication accuracy, and dimensional errors on the device performance are discussed. Additionally, manufacturing tolerances for three types of lithographic processes were calculated, serving as references for practical manufacturing purposes. [ABSTRACT FROM AUTHOR]

Purpose: Wafer bonding is a key process for 3 D advanced packaging of integrated circuits. It requires very high accuracy for the wafer alignment. To solve the problems of large movement stroke, position calibration error and low production efficiency in optical alignment, this paper aims to propose a new wafer magnetic alignment technology (MAT) which is based on tunnel magneto resistance effect. MAT can realize micro distance alignment and reduces the design and manufacturing difficulty of wafer bonding equipment. Design/methodology/approach: The current methods and existing problems of wafer optical alignment are introduced, and the mechanism and realization process of wafer magnetic alignment are proposed. Micro magnetic column (MMC) marks are designed on the wafer by the semiconductor manufacturing process. The mathematical model of the space magnetic field of the MMC is established, and the magnetic field distribution of the MMC alignment is numerically simulated and visualized. The relationship between the alignment accuracy and the MMC diameter, MMC remanence, MMC thickness and sensor measurement height was studied. Findings: The simulation analysis shows that the overlapping double MMCs can align the wafer with accuracy within 1 µm and can control the bonding distance within the micrometer range to improve the alignment efficiency. Originality/value: Magnetic alignment technology provides a new idea for wafer bonding alignment, which is expected to improve the accuracy and efficiency of wafer bonding. [ABSTRACT FROM AUTHOR]

The availability of thin-film lithium niobate on insulator (LNOI) and advances in processing have led to the emergence of fully integrated LiNbO3 electro-optic devices. Yet to date, LiNbO3 photonic integrated circuits have mostly been fabricated using non-standard etching techniques and partially etched waveguides, that lack the reproducibility achieved in silicon photonics. Widespread application of thin-film LiNbO3 requires a reliable solution with precise lithographic control. Here we demonstrate a heterogeneously integrated LiNbO3 photonic platform employing wafer-scale bonding of thin-film LiNbO3 to silicon nitride (Si3N4) photonic integrated circuits. The platform maintains the low propagation loss (<0.1 dB/cm) and efficient fiber-to-chip coupling (<2.5 dB per facet) of the Si3N4 waveguides and provides a link between passive Si3N4 circuits and electro-optic components with adiabatic mode converters experiencing insertion losses below 0.1 dB. Using this approach we demonstrate several key applications, thus providing a scalable, foundry-ready solution to complex LiNbO3 integrated photonic circuits. Lithium niobate plays an important role in integrated photonics, but its widespread application requires a reliable solution. Here, the authors present a wafer-scale approach to LNOI integration via wafer bonding to silicon nitride PICs. [ABSTRACT FROM AUTHOR]

In this letter, we present a photoreceiver front-end circuit that consists of an InP p-i-n photodetector (PIN PD) on an InP transimpedance amplifier (TIA) with double HBTs (DHBTs), in which the key integrated fabrication route of a transfer-printing (TP) process is introduced. Prior to integration, PDs and TIAs are individually fabricated on their respective wafers. Then, a discrete PD with only active layers is transferred onto the destination on a TIA wafer, thereafter, an on-chip coplanar waveguide connection is integrated. The PIN PD and DHBT TIA exhibit excellent performance, characterized by a responsivity of 0.51 A/W at $1.55~\mu \text{m}$ with a bandwidth of 20 GHz and a transimpedance gain of 36 dB $\Omega $ with a bandwidth of 27 GHz, respectively. Finally, the monolithically integrated circuit demonstrates a better frequency response by maximally reducing the parasitic effect, with an open clear eye diagram under a 20 Gb/s nonreturn-to-zero pattern, which evidently manifests its ability for ultrahigh-rate data operation. The present work, by employing a TP process, overcomes the issues in integrating discrete optoelectronic devices and proposes a unique approach for monolithic optoelectronic integrated circuit fabrication. [ABSTRACT FROM AUTHOR]

We employed creatively cold isostatic pressing technology to develop room-temperature bonding of Si–Si using 200-nm Au layers, which the ultra-high pressure was transmitted equally to Si–Si bonding samples by direct contact with the pressure medium during the cold isostatic pressing. We explored the influence of bonding pressure on the bonding rate. It was found that ultra-dense interconnects can be realized and the bonding rate increased with the increase of bonding pressure, which was attributed to the increased metal bond density. With the help of an excellent plastic deformation capacity of Au layers and ultra-high uniform isostatic pressing technology, a bonding rate of the whole 2-in. wafer reached 96.37% observed by scanning acoustic microscope. Simultaneously, in accord with the experiment results, we proposed the bonding mechanism model and discussed it in detail. Furthermore, taking laser lift-off as the front-end process, GaN HEMT devices were successfully transferred from sapphire to Si substrates with this method. Bonded GaN devices on Si substrate have been characterized. The dc characteristics showed an increase in the electrical performance of the GaN HEMT with maximum current density changing from 254 to 290 mA/mm. With the advantages of room-temperature bonding and without surface treatment, the technique was available in high-quality integration of chips. This room-temperature bonding via an ultra-high isostatic pressing strategy may inspire the development of a heterogeneous interconnection architecture and functional integrated circuits delivering a monolithic-like performance in the future hyper-scaling era. [ABSTRACT FROM AUTHOR]

Featured Application: Compact lasers integrated onto SOI for optical communications. The tremendous demand for low-cost, low-consumption and high-capacity optical transmitters in data centers challenges the current InP-photonics platform. The use of silicon (Si) photonics platform to fabricate photonic integrated circuits (PICs) is a promising approach for low-cost large-scale fabrication considering the CMOS-technology maturity and scalability. However, Si itself cannot provide an efficient emitting light source due to its indirect bandgap. Therefore, the integration of III-V semiconductors on Si wafers allows us to benefit from the III-V emitting properties combined with benefits offered by the Si photonics platform. Direct epitaxy of InP-based materials on 300 mm Si wafers is the most promising approach to reduce the costs. However, the differences between InP and Si in terms of lattice mismatch, thermal coefficients and polarity inducing defects are challenging issues to overcome. III-V/Si hetero-integration platform by wafer-bonding is the most mature integration scheme. However, no additional epitaxial regrowth steps are implemented after the bonding step. Considering the much larger epitaxial toolkit available in the conventional monolithic InP platform, where several epitaxial steps are often implemented, this represents a significant limitation. In this paper, we review an advanced integration scheme of AlGaInAs-based laser sources on Si wafers by bonding a thin InP seed on which further regrowth steps are implemented. A 3 µm-thick AlGaInAs-based MutiQuantum Wells (MQW) laser structure was grown onto on InP-SiO2/Si (InPoSi) wafer and compared to the same structure grown on InP wafer as a reference. The 400 ppm thermal strain on the structure grown on InPoSi, induced by the difference of coefficient of thermal expansion between InP and Si, was assessed at growth temperature. We also showed that this structure demonstrates laser performance similar to the ones obtained for the same structure grown on InP. Therefore, no material degradation was observed in spite of the thermal strain. Then, we developed the Selective Area Growth (SAG) technique to grow multi-wavelength laser sources from a single growth step on InPoSi. A 155 nm-wide spectral range from 1515 nm to 1670 nm was achieved. Furthermore, an AlGaInAs MQW-based laser source was successfully grown on InP-SOI wafers and efficiently coupled to Si-photonic DBR cavities. Altogether, the regrowth on InP-SOI wafers holds great promises to combine the best from the III-V monolithic platform combined with the possibilities offered by the Si photonics circuitry via efficient light-coupling. [ABSTRACT FROM AUTHOR]