A5028465639- GaN-based semiconductor devices and materials
- Semiconductor materials and devices
- Ga2O3 and related materials
- Thermal properties of materials
- Acoustic Wave Resonator Technologies
- ZnO doping and properties
- Silicon Carbide Semiconductor Technologies
- Ferroelectric and Piezoelectric Materials
- Metal and Thin Film Mechanics
- Advanced Battery Technologies Research
- Perovskite Materials and Applications
- Advanced Thermoelectric Materials and Devices
- Advanced battery technologies research
- Mechanical and Optical Resonators
- Advanced Photocatalysis Techniques
- Heat Transfer and Optimization
- Thermal Radiation and Cooling Technologies
- Coenzyme Q10 studies and effects
- 3D IC and TSV technologies
- Thin-Film Transistor Technologies
- Fuel Cells and Related Materials
- Advanced Fluorescence Microscopy Techniques
- Advanced ceramic materials synthesis
- Quantum Dots Synthesis And Properties
- Photorefractive and Nonlinear Optics
University of California, Los Angeles
2020-2024
UCLA Health
2023
California NanoSystems Institute
2020-2021
Monash University
2010-2021
University of California, Irvine
2018
Baker Heart and Diabetes Institute
2010-2015
Postfabrication surface treatment strategies have been instrumental to the stability and performance improvements of halide perovskite photovoltaics in recent years. However, a consensus understanding complex reconstruction processes occurring at is still lacking. Here, we combined complementary surface-sensitive depth-resolved techniques investigate mechanistic microscale level. We observed toward more PbI2-rich top induced by commonly used solvent isopropyl alcohol (IPA). discuss several...
Abstract Conventional epitaxy of semiconductor films requires a compatible single crystalline substrate and precisely controlled growth conditions, which limit the price competitiveness versatility process. We demonstrate substrate-tolerant nano-heteroepitaxy (NHE) high-quality formamidinium-lead-tri-iodide (FAPbI 3 ) perovskite films. The layered templates solid-state phase conversion FAPbI from its hexagonal non-perovskite to cubic polymorph, where kinetics are by synergistic effect...
High thermal conductivity materials show promise for mitigation and heat removal in devices. However, shrinking the length scales of these often leads to significant reductions conductivities, thus invalidating their applicability functional In this work, we report on high in-plane conductivities 3.05, 3.75, 6 μm thick aluminum nitride (AlN) films measured via steady-state thermoreflectance. At room temperature, AlN possess an ∼260 ± 40 W m–1 K–1, one highest reported date any thin film...
The ultrawide band gap, high breakdown electric field, and large-area affordable substrates make β-Ga2O3 promising for applications of next-generation power electronics, while its thermal conductivity is at least 1 order magnitude lower than other wide/ultrawide gap semiconductors. To avoid the degradation device performance reliability induced by localized Joule-heating, proper management strategies are essential, especially high-power high-frequency applications. This work reports a...
Summary This work reports a 50.74 GHz lithium niobate (LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> ) acoustic resonator with high quality factor (Q) of 237 and an electromechanical coupling (k <sup xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> 5.17% resulting in figure merit (FoM, Q•k 12.2. The LiNbO employs novel bilayer periodically poled piezoelectric film (P3F) 128º Y-cut on amorphous silicon (a-Si) sapphire stack to...
Heat dissipation plays a crucial role in the performance and reliability of high-power GaN-based electronics. While AlN transition layers are commonly employed heteroepitaxial growth GaN-on-SiC substrates, concerns have been raised about their impact on thermal transport across GaN/SiC interfaces. In this study, we present experimental measurements boundary conductance (TBC) interfaces with varying thicknesses layer (ranging from 0 to 73 nm) at different temperatures. Our findings reveal...
This paper reports an acoustic resonator at 57 GHz with a high electromechanical coupling $(k^{2})$ of 7.3% and 3-dB quality factor (Q) 56, collectively enabling record-breaking Figure merit $(\mathrm{F}\mathrm{o}\mathrm{M},\ Q\cdot k^{2})$ 4.1, order magnitude higher than the state-of-the-art resonators. The device leverages third-order antisymmetric (A3) Lamb mode in 110 nm 128°Y-cut lithium niobate (LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML"...
This work reports an acoustic filter at 23.5 GHz with a low insertion loss (IL) of 2.38 dB and 3-dB fractional bandwidth (FBW) 18.2%, significantly surpassing the state-of-the-art. The device leverages electrically coupled resonators in 100 nm 128° Y-cut lithium niobate (LiNbO3) piezoelectric thin film, operating first-order antisymmetric (A1) mode. A new film stack, namely transferred thin-film LiNbO3 on silicon (Si) substrate intermediate amorphous (a-Si) layer, facilitates record-breaking...
Wide and ultrawide bandgap semiconductors, such as GaN, play a crucial role in high-power applications, yet their performance is often constrained by thermal management challenges. In this work, we introduce high-quality interface between GaN AlN, prepared through wafer-scale bonding verified via high-resolution transmission electron microscopy transport experiments. We experimentally measured the boundary conductance of GaN–AlN interface, achieving up to 320 MW/m2K at room temperature using...
AlN is an ultra-wide bandgap semiconductor which has been developed for applications including power electronics and optoelectronics. Thermal management of these the key stable device performance allowing long lifetimes. AlN, with its potentially high thermal conductivity, can play important role serving as a dielectric layer, growth substrate, heat spreader to improve performance. However, intrinsic conductivity bulk predicted by theoretical calculations not experimentally observed because...
Abstract We report on high-quality n -Al 0.87 Ga 0.13 N-A 0.64 0.36 N heterostructures over single crystal AlN. For these pseudomorphic heterostructures, high-resolution X-ray and Topographic analysis was used to establish a threading dislocation density of 7 × 10 3 cm −2 . Using reverse composition graded + x 1- contact layers, we obtained linear ohmic contacts with 4.3 Ω mm specific resistance. A critical breakdown field >11 MV −1 also measured. In combination the channel resistance...
This work presents the first demonstration of a three layer periodically poled piezoelectric film (P3F) lithium niobate resonator. The proposed platform allows for high series 3dB quality factor (Q) resonances, including Q up to 811 at 12.98 GHz. trilayer stack employs use layers with alternating orientations on an intermediate amorphous bonding and sapphire substrate. enables order Lamb modes thanks comparatively large thickness when compared monolayer counterparts. shows ultra $f\dot Q$...
SummaryThis paper reports a method of frequency scaling millimeter wave thin-film lithium niobate (LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> ) acoustic resonators using ion beam assisted Argon gas cluster trimming whilst maintaining high figure merit (FoM) and averting ultra-thin-film fabrication difficulties. A transferred 100 nm thick 128° Y-cut LiNbO thin film is trimmed to thickness 75 nm. Consequently, 24.4 GHz...
Annealing Mg-implanted homoepitaxial GaN at temperatures above 1400 °C eliminates the formation of inversion domains and leads to improved dopant activation efficiency. Extended defects, in form domains, contain electrically inactive Mg after post-implantation annealing as high 1300 (one GPa N2 overpressure), which results a low Triple-axis x-ray data reveal that implant-induced strain is fully relieved for 10 min, indicating strain-inducing point defects formed during implantation have...
Gallium nitride (GaN) has emerged as a quintessential wide band-gap semiconductor for an array of high-power and high-frequency electronic devices. The phonon thermal resistances that arise in GaN thin films can result detrimental performances these applications. In this work, we report on the conductivity submicrometer micrometer thick homoepitaxial grown via two different techniques (metal-organic chemical vapor deposition molecular beam epitaxy) measured (time domain thermoreflectance...
Smooth (&lt; 0.5 nm rms) and subsurface damage-free (010) β-Ga2O3 was achieved with low-pressure chemical mechanical polishing. An applied pressure of 1 kPa along colloidal silica poromeric polyurethane polishing pads rotating at 30 rpm found to be the optimal parameters for β-Ga2O3. Using higher pressures typically employed in current literature induced damage substrates. Diffuse scatter intensity triple-axis x-ray rocking curves used determine presence lattice damage, which quantified...
The evolution of defects due to high‐pressure annealing magnesium ion‐implanted epitaxial GaN grown on high‐quality substrates is investigated. Changes in the implant‐induced strain are quantified as a function temperature and time. After at 1300 °C for 10 min, fully relieved accompanied by presence extended such basal plane stacking faults prismatic loops. Approximately one‐third original remains after 700 °C, 5% 1000 100 min. In all cases, nearly recovered occurs within first few minutes...
The thermal properties of semiconductors following exposure to ion irradiation are great interest for the cooling electronic devices; however, gradients in composition and structure due often make measurement difficult. Furthermore, nature spatial variations resistances spatially varying damage is not well understood. In this work, we develop an advancement analysis time-domain thermoreflectance account conductivity a material resulting from distribution defects. We then use method measure...
The impact of postbond annealing on the structural and thermal characteristics 130 nm thick exfoliated (201) β-Ga2O3 (via H+ ion implantation) wafer bonded to (0001) 4H-SiC was studied. Thirty nanometer amorphous-Al2O3 grown substrates prior bonding as an interlayer between 4H-SiC. surface activated technique utilized for bonding, which induces a thin amorphous interfacial region at interface (Al2O3|4H-SiC). We demonstrate structure 800 °C up 1 h is beneficial: (1) removal residual strain in...
The effect of heteroepitaxial β-(AlxGa1−x)2O3 film thickness and Al content on surface morphology was characterized to experimentally determine the critical limitations (010) β-(AlxGa1−x)2O3/Ga2O3 heterostructure. High-resolution x-ray diffraction used assess strain state films; reciprocal space mapping (RSM) revealed that even cracked films were still fully strained. In films, diffuse scattering observed in RSMs, indicating lattice tilting. Cracking investigated using atomic force...
Defect reporting customarily exists in most applications and web sites to support issue by end users for developers receive actionable feedback. However, the impact of "human-centric" issues - such as age, gender, language, culture, physical mental challenges, socio-economic status is often overlooked development process during product inception defect reporting. Most tools lack necessary human-centric features enable a challenged user adequately navigate report defects i.e. do not take into...
In this work, synchrotron monochromatic X-ray topography was employed to study the structural characteristics of as-received c-plane dot-core GaN substrates and then investigate evolution with annealing under growth-like conditions at 1050 °C for 10 h. Single exposure images were obtained using (11 2 4) asymmetric reflection. These superimposed quantify lattice distortions in regions near dot-cores between these defects. The results show that different from same vendor exhibit defect...