Multi-chip heterogeneously integrated array of active three-terminal transistor lasers and passive photonic structures for electronic-photonic integration on silicon
Title: Multi-chip heterogeneously integrated array of active three-terminal transistor lasers and passive photonic structures for electronic-photonic integration on silicon
An array of active photonic devices is fabricated in unison after a heterogeneous integration process first metal-eutectically bonds these distinct materials as a distribution onto a silicon host wafer. The patterning out of heterogeneous materials followed by the formation of all photonic devices allows for wide-area fine-alignment without the need for discrete die alignment or placement. The integration process is designed as a CMOS-compatible, scalable method for bringing together distinct III-V epitaxial structures and optical-waveguiding epitaxial structures, demonstrating the capabilities of forming a multi-chip layer of photonic materials. Integrated GaAs-based vertical light-emitting transistors (LET) are designed and fabricated as the active devices whose third electrical terminal provides an electrical interconnect and thermal dissipation path to the silicon host wafer. The performance of these devices as both electrical transistors and spontaneous-emission optical devices is compared to their monolithically-integrated counterparts to investigate improvements in device characteristics when integrated onto silicon. The fabrication methods are modified and optimized for thin-film transferred materials and are then extended to transistor laser (TL) fabrication. Passive waveguiding structures are designed and simulated for coupling light from the active devices, and their fabrication scheme is presented such that it can be similarly performed with transferred materials. Work toward the demonstration of integrated transistor lasers is shown to represent progress toward an electronic-photonic circuit network. The combination of heterogeneous integration with three-terminal photonic structures enables an elegant solution to both packaging and signal interconnect constraints for the implementation of photonic logic in silicon photonics systems. more »« less
Espenhahn, Leah; Carlson, John; Su, Patrick; Dallesasse, John M.
(, Proceedings Volume 12020, Vertical-Cavity Surface-Emitting Lasers XXVI)
Choquette, Kent D.; Lei, Chun; Graham, Luke A.
(Ed.)
A wafer-scale CMOS-compatible process for heterogeneous integration of III-V epitaxial material onto silicon for photonic device fabrication is presented. Transfer of AlGaAs-GaAs Vertical-Cavity Surface-Emitting Laser (VCSEL) epitaxial material onto silicon using a carrier wafer process and metallic bonding is used to form III-V islands which are subsequently processed into VCSELs. The transfer process begins with the bonding of III-V wafer pieces epitaxy-down on a carrier wafer using a temporary bonding material. Following substrate removal, precisely-located islands of material are formed using photolithography and dry etching. These islands are bonded onto a silicon host wafer using a thin-film non-gold metal bonding process and the transfer wafer is removed. Following the bonding of the epitaxial islands onto the silicon wafer, standard processing methods are used to form VCSELs with non-gold contacts. The removal of the GaAs substrate prior to bonding provides an improved thermal pathway which leads to a reduction in wavelength shift with output power under continuous-wave (CW) excitation. Unlike prior work in which fullyfabricated VCSELs are flip-chip bonded to silicon, all photonic device processing takes place after the epitaxial transfer process. The electrical and optical performance of heterogeneously integrated 850nm GaAs VCSELs on silicon is compared to their as-grown counterparts. The demonstrated method creates the potential for the integration of III-V photonic devices with silicon CMOS, including CMOS imaging arrays. Such devices could have use in applications ranging from 3D imaging to LiDAR.
Carlson, John A.; Dallesasse, John M.
(, Conference on Lasers and Electro-Optics, OSA Technical Digest)
An array of heterogeneously integrated light-emitting transistors is fabricated after an epitaxial transfer process bonds and interconnects active III-V photonic material onto a CMOS- compatible host wafer for the purposes of establishing a photonic logic network.
Dallesasse, John M.; Carlson, John A.; Ganjoo, Manaav; Espenhahn, Leah
(, 2021 5th IEEE Electron Devices Technology & Manufacturing Conference (EDTM))
null
(Ed.)
Enhancing the functionality of silicon through the integration of other materials such as III-V semiconductors has been recognized as a path to overcoming limitations imposed by characteristics fundamental to silicon's material physics while still capitalizing on properties that have enabled the success of the global integrated circuit industry [1]–[2][3]. High-speed electronic devices, devices with high breakdown voltages, light emitting/detecting devices, and devices for photon control can all be integrated with conventional CMOS to perform specialized electronic or photonic functions if suitable methods for forming such heterogeneously integrated regions are available that provide high yield and are compatible with fabrication processes that occur subsequent to the heterogeneous integration process. Technical challenges include lattice mismatch, thermal expansion coefficient differences, having the capability to form low-resistance electrical contacts using materials that are compatible with CMOS, more generally managing cross-contamination in tools used for front-end-of-line processing after III-V regions are established on the silicon wafers, and thermal management for the heterogeneously integrated devices or circuits. These together create formidable obstacles, but there is also the obstacle of defining a business case for creating hybrid wafer fabs given the applications that would be served by ICs with enhanced functionality. Bringing functions that are off chip onto the chip needs to be justified both technically and financially.
III-Nitride light-emitting diodes (LEDs) and laser diodes (LDs) are light sources covering ultraviolet (UV) and visible spectral regimes, which offer benefits including compact size, wavelength tuning, long lifetime, and sustainability. UV light sources have a range of applications in the fields of biology and medicine, such as sterilization and the purification of both water and air, where visible light emitters have been used in miniaturized photonic devices for optogenetic applications and other light-based therapies. Those III-Nitride light sources provide tremendous potential to be integrated with silicon (Si)-based lab-on-a-chip (LOC) technology, which typically requires the coupling of an external light source through fiber optic cable, limiting the field deployment of the devices. Integrating an on-chip III-Nitride light source with these devices opens the door to complete LOC technology, allowing for the simultaneous detection of multiple bio agents on a single platform without the need for external photonic sources. While most integrated microsystems still rely on wafer bonding at the device or wafer level, one promising method to achieve the integration of III-nitride UV and visible LEDs and LDs with conventional Si photonics and complementary metal-oxide-semiconductor (CMOS) platforms is through the use of micro-transfer printing (µTP). µTP has greater tolerances in alignment than techniques such as flip-chip integration and allows for the transfer of many devices at once. Additionally, the µTP process does not call for the complex and high temperature processing required for standard wafer bonding or necessitate complicated growth and lattice matching needed for monolithic integration. To enable µTP, an elastomeric, such as polydimethylsiloxane (PDMS), is utilized to create a transfer stamp that is employed for the precise selection of fabricated semiconductor devices for transfer from a source wafer to a target wafer. III-Nitride LEDs or LDs epitaxial structures are grown on a source wafer and fabricated through the creation of tethered coupons, or individual devices. This is accomplished by utilizing III-nitride materials grown on (111) Si. These devices can be fabricated through standard lithography and etching processes, etching down to the (111) Si substrate. A larger mesa can be patterned and etched into the Si substrate, exposing the sidewalls for wet chemical etching. The finished devices are then encapsulated in SiNxthrough plasma enhanced chemical vapor deposition (PECVD), which is patterned through standard lithography to define tethers and anchors for the subsequent wet etch. The fabricated devices are oriented in such a way as to take advantage of the difference in etch rates (>100x) of Si(110) and Si(111) in potassium hydroxide (KOH), where etching proceeds along the <110> direction. After KOH etching, the devices are left encapsulated in SiNxand suspended over the silicon substrate with an air gap, while the anchors and tethers are left largely unaffected.This enables the elastomer stamp to press down, breaking the tethers, and releasing the device. The stamp is then able to transfer the device to a target wafer that has been coated and patterned with InterVia, a spin-on dielectric material that acts as an adhesion layer. The stamp is pressed into the target wafer in such a way that the device is adhered to the target and released from the elastomer stamp. This technique can be applied to LEDs and LDs grown on (111) Si, allowing for the heterogeneous integration of III-nitride LED and LDs with conventional CMOS and Si photonic integrated circuits (PICs) as on-chip light sources, opening the door to complete LOC technology without the need for additional external photonic sources.
Chakravarty, Swapnajit; Midkiff, Jason; Yoo, Kyoungmin; Chung, Chi-Jui; Rostamian, Ali; Chen, Ray T.; García-Blanco, Sonia M.; Cheben, Pavel
(, Proceedings of the SPIE)
Chemicals are best recognized by their unique wavelength specific optical absorption signatures in the molecular fingerprint region from λ=3-15μm. In recent years, photonic devices on chips are increasingly being used for chemical and biological sensing. Silicon has been the material of choice of the photonics industry over the last decade due to its easy integration with silicon electronics as well as its optical transparency in the near-infrared telecom wavelengths. Silicon is optically transparent from 1.1 μm to 8 μm with research from several groups in the mid-IR. However, intrinsic material losses in silicon exceed 2dB/cm after λ~7μm (~0.25dB/cm at λ=6μm). In addition to the waveguiding core, an appropriate transparent cladding is also required. Available core-cladding choices such as Ge-GaAs, GaAs-AlGaAs, InGaAs-InP would need suspended membrane photonic crystal waveguide geometries. However, since the most efficient QCLs demonstrated are in the InP platform, the choice of InGaAs-InP eliminates need for wafer bonding versus other choices. The InGaAs-InP material platform can also potentially cover the entire molecular fingerprint region from λ=3-15μm. At long wavelengths, in monolithic architectures integrating lasers, detectors and passive sensor photonic components without wafer bonding, compact passive photonic integrated circuit (PIC) components are desirable to reduce expensive epi material loss in passive PIC etched areas. In this paper, we consider miniaturization of waveguide bends and polarization rotators. We experimentally demonstrate suspended membrane subwavelength waveguide bends with compact sub-50μm bend radius and compact sub-300μm long polarization rotators in the InGaAs/InP material system. Measurements are centered at λ=6.15μm for sensing ammonia
Carlson, John A., and Dallesasse, John M. Multi-chip heterogeneously integrated array of active three-terminal transistor lasers and passive photonic structures for electronic-photonic integration on silicon. Retrieved from https://par.nsf.gov/biblio/10379669. Proceedings Volume 11285, Silicon Photonics XV 11285. Web. doi:10.1117/12.2544009.
Carlson, John A., & Dallesasse, John M. Multi-chip heterogeneously integrated array of active three-terminal transistor lasers and passive photonic structures for electronic-photonic integration on silicon. Proceedings Volume 11285, Silicon Photonics XV, 11285 (). Retrieved from https://par.nsf.gov/biblio/10379669. https://doi.org/10.1117/12.2544009
Carlson, John A., and Dallesasse, John M.
"Multi-chip heterogeneously integrated array of active three-terminal transistor lasers and passive photonic structures for electronic-photonic integration on silicon". Proceedings Volume 11285, Silicon Photonics XV 11285 (). Country unknown/Code not available. https://doi.org/10.1117/12.2544009.https://par.nsf.gov/biblio/10379669.
@article{osti_10379669,
place = {Country unknown/Code not available},
title = {Multi-chip heterogeneously integrated array of active three-terminal transistor lasers and passive photonic structures for electronic-photonic integration on silicon},
url = {https://par.nsf.gov/biblio/10379669},
DOI = {10.1117/12.2544009},
abstractNote = {An array of active photonic devices is fabricated in unison after a heterogeneous integration process first metal-eutectically bonds these distinct materials as a distribution onto a silicon host wafer. The patterning out of heterogeneous materials followed by the formation of all photonic devices allows for wide-area fine-alignment without the need for discrete die alignment or placement. The integration process is designed as a CMOS-compatible, scalable method for bringing together distinct III-V epitaxial structures and optical-waveguiding epitaxial structures, demonstrating the capabilities of forming a multi-chip layer of photonic materials. Integrated GaAs-based vertical light-emitting transistors (LET) are designed and fabricated as the active devices whose third electrical terminal provides an electrical interconnect and thermal dissipation path to the silicon host wafer. The performance of these devices as both electrical transistors and spontaneous-emission optical devices is compared to their monolithically-integrated counterparts to investigate improvements in device characteristics when integrated onto silicon. The fabrication methods are modified and optimized for thin-film transferred materials and are then extended to transistor laser (TL) fabrication. Passive waveguiding structures are designed and simulated for coupling light from the active devices, and their fabrication scheme is presented such that it can be similarly performed with transferred materials. Work toward the demonstration of integrated transistor lasers is shown to represent progress toward an electronic-photonic circuit network. The combination of heterogeneous integration with three-terminal photonic structures enables an elegant solution to both packaging and signal interconnect constraints for the implementation of photonic logic in silicon photonics systems.},
journal = {Proceedings Volume 11285, Silicon Photonics XV},
volume = {11285},
author = {Carlson, John A. and Dallesasse, John M.},
editor = {Reed, Graham T. and Knights, Andrew P.}
}
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