Heterogeneous integration technology for the thermal management of Ga_(2)O_(3) power devices

The more severe phonon-phonon scattering in gallium oxide(Ga_(2)O_(3)) crystals leads to lower thermal conductivity compared to most other semiconductor materials. To address this issue and enhance the heat dissipation in Ga_(2)O_(3) devices, one practical solution is to integrate Ga_(2)O_(3) with a highly thermally conductive substrate, such as SiC and Si. Currently,there are three methods employed for the heterogeneous integration of Ga_(2)O_(3) with highly thermally conductive substrates:mechanical exfoliation, hetero-epitaxy growth, and ion-cutting technique.

Formation of multifaceted nano-groove structure on rutile TiO_(2) photoanode for efficient electron-hole separation and water splitting

Photoelectrochemical(PEC)water-splitting using solar energy holds great promise for the renewable energy future,and a key challenge in the development of industry viable PEC devices is the unavailability of high-efficient photoanodes.Herein,we designed a TiO_(2) model photocatalyst with nano-groove pattern and different surface orientation using low-energy Ar+irradiation and photoetching of TiO_(2),and significantly improved the intrinsic activity for PEC water oxidation.High-resolution transmission electron microscopy directly manifests that the grooves consist of highly stepped surface with<110>steps and well-crystallized.Transient absorption spectroscopy reveals the groove surface that allows for increased recovery lifetime,which ensures promoted electron-hole separation efficiency.Surface photovoltage directly shows the carrier separation and transportation behaviors,verified by selective photodeposition,demonstrating the groove surface on TiO_(2) contributes to electron-hole separation.This work proposes an efficient and scalable photoanode strategy,which potentially can open new opportunities for achieving efficient PEC water oxidation performance.

Stress and strain analysis of Si-based Ⅲ-V template fabricated by ion-slicing

Strain and stress were simulated using finite element method(FEM)for threeⅢ-V-on-Insulator(Ⅲ-VOI)structures,i.e.,InP/SiO2/Si,InP/Al2O3/SiO2/Si,and GaAs/Al2O3/SiO2/Si,fabricated by ion-slicing as the substrates for optoelectronic devices on Si.The thermal strain/stress imposes no risk for optoelectronic structures grown on InPOI at a normal growth temperature using molecular beam epitaxy.Structures grown on GaAsOI are more dangerous than those on InPOI due to a limited critical thickness.The intermedia Al2O3 layer was intended to increase the adherence while it brings in the largest risk.The simulated results reveal thermal stress on Al2O3 over 1 GPa,which is much higher than its critical stress for interfacial fracture.InPOI without an Al2O3 layer is more suitable as the substrate for optoelectronic integration on Si.

氧化镓异质集成和异质结功率晶体管研究进展

超宽禁带氧化镓(Ga_(2)O_(3))半导体具有临界击穿场强高和可实现大尺寸单晶衬底等优势,在功率电子和微波射频器件方面具有重要的研究价值和广阔的应用前景.尽管Ga_(2)O_(3)材料与器件研究已取得很大进展,但其极低的热导系数和缺少有效的p型掺杂方法成为限制其复杂器件结构制备和器件性能提升的主要瓶颈.针对上述两大关键瓶颈,本文综述了利用异质材料集成的方法实现高导热衬底Ga_(2)O_(3)异质集成晶体管与基于p型氧化镍/n型氧化镓(p-NiO/n-Ga_(2)O_(3))异质结的Ga_(2)O_(3)功率二极管和超结晶体管的研究进展.采用离子刀智能剥离-键合技术实现的高导热衬底Ga_(2)O_(3)异质集成方案可有效解决其导热问题,碳化硅(SiC)和硅(Si)基Ga_(2)O_(3)异质集成晶体管展现出远优于Ga_(2)O_(3)体材料器件的热相关特性.采用异质外延技术制备的p-NiO/n-Ga_(2)O_(3)功率二极管和超结晶体管均展现出良好的电学特性,p-NiO/n-Ga_(2)O_(3)异质结为Ga_(2)O_(3)双极器件的发展提供了一种可行途径.异质集成和异质结技术可有效地克服Ga_(2)O_(3)本身的关键难点问题,助力高效能、高功率和商业可扩展的Ga_(2)O_(3)微电子系统的实现,推动其实用化进程.

Si-based InGaAs photodetectors on heterogeneous integrated substrate

In this paper,InGaAs p-i-n photodetectors(PDs)on an InP/SiO2/Si(InPOI)substrate fabricated by ion-slicing technology are demonstrated and compared with the identical device on a commercial InP substrate.The quality of epitaxial layers on the InPOI substrate is similar to that on the InP substrate.The photo responsivities of both devices measured at 1.55μm are comparable,which are about 0.808-0.828 A W^(-1).Although the dark current of PD on the InPOI substrate is twice as high as that of PD on the InP substrate at 300 K,the peak detectivities of both PDs are comparable.In general,the overall performance of the InPOI-based PD is comparable to the InP-based PD,demonstrating that the ion-slicing technology is a promising route to enable the highquality Si-based InP platform for the full photonic integration on a Si substrate.

Efficient thermal dissipation in wafer-scale heterogeneous integration of single-crystalline𝛽β-Ga_(2)O_(3)thin film on SiC

The semiconductor,β-Ga_(2)O_(3)is attractive for applications in high power electronic devices with low conduction loss due to its ultra-wide bandgap(∼4.9 eV)and large Baliga’s figure of merit.However,the thermal conductivity of𝛽β-Ga_(2)O_(3)is much lower than that of other wide/ultra-wide bandgap semiconductors,such as SiC and GaN,which results in the deterioration of𝛽β-Ga_(2)O_(3)-based device performance and reliability due to self-heating.To overcome this problem,a scalable thermal management strategy was proposed by heterogeneously integrating wafer-scale single-crystalline𝛽β-Ga_(2)O_(3)thin films on a highly thermally conductive SiC substrate.Characterization of the transferred𝛽β-Ga_(2)O_(3)thin film indicated a uniform thickness to within±2.01%,a smooth surface with a roughness of 0.2 nm,and good crystalline quality with an X-ray rocking curves(XRC)full width at half maximum of 80 arcsec.Transient thermoreflectance measurements were employed to investigate the thermal properties.The thermal performance of the fabricated𝛽β-Ga_(2)O_(3)/SiC heterostructure was effectively improved in comparison with that of the𝛽β-Ga_(2)O_(3)bulk wafer,and the effective thermal boundary resistance could be further reduced to 7.5 m 2 K/GW by a post-annealing process.Schottky barrier diodes(SBDs)were fabricated on both a𝛽β-Ga_(2)O_(3)/SiC heterostructured material and a𝛽β-Ga_(2)O_(3)bulk wafer.Infrared thermal imaging revealed the temperature increase of the SBDs on𝛽β-Ga_(2)O_(3)/SiC to be one quarter that on the𝛽β-Ga_(2)O_(3)bulk wafer with the same applied power,which suggests that the combination of the𝛽-Ga_(2)O_(3)thin film and SiC substrate with high thermal conductivity promotes heat dissipation in𝛽β-Ga_(2)O_(3)-based devices.

Waveguide-coupled deterministic quantum light sources and post-growth engineering methods for integrated quantum photonics

Integrated photonic quantum circuits(IPQCs)have attracted increasing attention in recent years due to their widespread applications in quantum information science.While the most envisioned quantum technologies such as quantum communications,quantum computer and quantum simulations have placed a strict constraint on the scalability of chip-integrated quantum light sources.By introducing sizeconfined nanostructures or crystal imperfections,low-dimensional semiconductors have been broadly explored as chip-scale deterministic single-photon sources(SPSs).Thus far a variety of chip-integrated deterministic SPSs have been investigated across both monolithic and hybrid photonic platforms,including molecules,quantum dots,color centers and two-dimensional materials.With the rapid development of the chip-scale generation of single photons with deterministic quantum emitters,the field of IPQCs has raised new challenges and opportunities.In this paper,we highlight recent progress in the development of waveguide-coupled deterministic SPSs towards scalable IPQCs,and review the post-growth tuning techniques that are specifically developed to engineer the optical properties of these WG-coupled SPSs.Future prospects on stringent requirement for the quantum engineering toolbox in the burgeoning field of integrated photonics are also discussed.

High-Q microresonators on 4H-silicon-carbide-on-insulator platform for nonlinear photonics

The realization of high-quality(Q)resonators regardless of the underpinning material platforms has been a ceaseless pursuit,because the high-Q resonators provide an extreme environment for confining light to enable observations of many nonlinear optical phenomenon with high efficiencies.Here,photonic microresonators with a mean Q factor of 6.75×10^(6)were demonstrated on a 4H-silicon-carbide-on-insulator(4H-SiCOI)platform,as determined by a statistical analysis of tens of resonances.Using these devices,broadband frequency conversions,including second-,third-,and fourth-harmonic generations have been observed.Cascaded Raman lasing has also been demonstrated in our SiC microresonator for the first time,to the best of our knowledge.Meanwhile,by engineering the dispersion properties of the SiC microresonator,we have achieved broadband Kerr frequency combs covering from 1300 to 1700nm.Our demonstration represents a significant milestone in the development of SiC photonic integrated devices.

Emerging material platforms for integrated microcavity photonics

Many breakthroughs in technologies are closely associated with the deep understanding and development of new material platforms.As the main material used in microelectronics,Si also plays a leading role in the development of integrated photonics.The indirect bandgap,absence ofχ(2)nonlinearity and the parasitic nonlinear absorptions at the telecom band of Si imposed technological bottlenecks for further improving the performances and expanding the functionalities of Si microcavities in which the circulating light intensity is dramatically amplified.The past two decades have witnessed the burgeoning of the novel material platforms that are compatible with the complementary metal-oxide-semiconductor(COMS)process.In particular,the unprecedented optical properties of the emerging materials in the thin film form have resulted in revolutionary progress in microcavity photonics.In this review article,we summarize the recently developed material platforms for integrated photonics with the focus on chip-scale microcavity devices.The material characteristics,fabrication processes and device applications have been thoroughly discussed for the most widely used new material platforms.We also discuss open challenges and opportunities in microcavity photonics,such as heterogeneous integrated devices,and provide an outlook for the future development of integrated microcavities.

Superconducting microstrip single-photon detector with system detection efficiency over 90%at 1550 nm

Generally,a superconducting nanowire single-photon detector(SNSPD)is composed of wires with a typical width of∼100 nm.Recent studies have found that superconducting strips with a micrometer-scale width can also detect single photons.Compared with the SNSPD covering the same area,the superconducting microstrip single-photon detector(SMSPD)has smaller kinetic inductance,higher working current,and lower requirements in fabrication accuracy,providing potential applications in the development of ultralarge active area detectors.However,the study of SMSPD is still in its infancy,and the realization of its high-performance and practical use remains an open question.This study demonstrates a NbN SMSPD with a nearly saturated system detection efficiency(SDE)of∼92.2%at a dark count rate of∼200 cps,a polarization sensitivity of∼1.03,and a minimum timing jitter of∼48 ps at the telecom wavelength of 1550 nm when coupled with a single-mode fiber and operated at 0.84 K.Furthermore,the detector’s SDE is over 70%when operated at a 2.1 K closed-cycle cryocooler.

β-Ga2O3 MOSFETs on the Si substrate fabricated by the ion-cutting process

β-Ga2O3 MOSFETs are demonstrated on heterogeneous Ga2O3-Al2O3-Si(GaOISi)substrate fabricated by ion-cutting process.Enhancement(E)-and depletion(D)-modeβ-Ga2O3 transistors are realized on by varying the channel thickness(Tch).E-mode GaOISi transistor with a Tchof 15 nm achieves a high threshold voltage VTHof^8 V.With the same T increase,GaOISi transistors demonstrate more stable ON-current IONand OFF-current IOFFperformance compared to the reported devices on bulk Ga2O3 wafer.Transistors on GaOISi achieve the breakdown voltage of 522 and 391 V at 25°C and 200°C,respectively.

Soliton formation and spectral translation into visible on CMOS-compatible 4H-silicon-carbide-oninsulator platform

Recent advancements in integrated soliton microcombs open the route to a wide range of chip-based communication,sensing,and metrology applications.The technology translation from laboratory demonstrations to real-world applications requires the fabrication process of photonics chips to be fully CMOS-compatible,such that the manufacturing can take advantage of the ongoing evolution of semiconductor technology at reduced cost and with high volume.Silicon nitride has become the leading CMOS platform for integrated soliton devices,however,it is an insulator and lacks intrinsic second-order nonlinearity for electro-optic modulation.Other materials have emerged such as AlN,LiNbO_(3),AlGaAs and GaP that exhibit simultaneous second-and third-order nonlinearities.Here,we show that silicon carbide(SiC)--already commercially deployed in nearly ubiquitous electrical power devices such as RF electronics,MOSFET,and MEMS due to its wide bandgap properties,excellent mechanical properties,piezoelectricity and chemical inertia--is a new competitive CMOS-compatible platform for nonlinear photonics.High-quality-factor microresonators(Q=4×10^(6))are fabricated on 4H-SiC-on-insulator thin films,where a single soliton microcomb is generated.In addition,we observe wide spectral translation of chaotic microcombs from near-infrared to visible due to the second-order nonlinearity of SiC.Our work highlights the prospects of SiC for future low-loss integrated nonlinear and quantum photonics that could harness electro-opto-mechanical interactions on a monolithic platform.

Ultra-dense planar metallic nanowire arrays with extremely large anisotropic optical and magnetic properties

A nanofabrication method for the production of ultra-dense planar metallic nanowire arrays scalable to wafer-size is presented. The method is based on an efficient template deposition process to grow diverse metallic nanowire arrays with extreme regularity in only two steps. First, Ⅲ-Ⅴ semiconductor substrates are irradiated by a low-energy ion beam at an elevated temperature, forming a highly ordered nanogroove pattern by a ＂reverse epitaxy＂ process due to self-assembly of surface vacancies. Second, diverse metallic nanowire arrays （Au, Fe, Ni, Co, FeAl alloy） are fabricated on these Ⅲ-Ⅴ templates by deposition at a glancing incidence angle. This method allows for the fabrication of metallic nanowire arrays with periodicities down to 45 nm scaled up to wafer-size fabrication. As typical noble and magnetic metals, the Au and Fe nanowire arrays produced here exhibited large anisotropic optical and magnetic properties, respectively. The excitation of localized surface plasmon resonances （LSPRs） of the Au nanowire arrays resulted in a high electric field enhancement, which was used to detect phthalocyanine （CoPc） in surface-enhanced Raman scattering （SERS）. Furthermore, the Fe nanowire arrays showed a very high in-plane magnetic anisotropy of approximately 412 mT, which may be the largest in-plane magnetic anisotropy field yet reported that is solely induced via shape anisotropy within the plane of a thin film.