About

Sriram Krishnamoorthy is an Associate Professor in the Department of Materials at the University of California, Santa Barbara. His research group operates at the intersection of materials, electrical engineering, and physics, focusing on the study and engineering of next-generation (ultra)wide band gap semiconductors such as Gallium Oxide. His work encompasses epitaxial growth, electronic transport, design and modeling, micro/nano fabrication, and characterization of electronic and optoelectronic devices. These devices are developed for a broad range of applications including power electronics, high-frequency electronics, and ultraviolet optoelectronics. Dr. Krishnamoorthy holds a Ph.D. in Electrical Engineering from The Ohio State University, an M.Sc. (Hons) in Physics, and a B.E. (Hons.) in Electrical and Electronics Engineering from Birla Institute of Technology & Science (BITS)-Pilani.

Research topics

• Materials science
• Optoelectronics
• Nanotechnology
• Chemistry
• Composite material
• Condensed matter physics
• Engineering
• Electrical engineering
• Optics
• Physics
• Computer Science
• Crystallography
• Management science
• Metallurgy
• Simulation
• Data science
• Chemical engineering
• Computational science
• Engineering physics
• Computational chemistry

Selected publications

• β-Ga2O3 MOSFETs on highly uniform 2-in. unintentionally doped vertical Bridgman substrates

  Journal of Vacuum Science & Technology A Vacuum Surfaces and Films · 2026-04-24

  article

  Beta-phase gallium oxide (β-Ga2O3) is a promising ultra-wide-bandgap (UWBG) semiconductor for next-generation high-power electronics. A critical challenge for commercialization is validating the material quality and uniformity of large-area substrates. In this work, the material quality of a 2-in. unintentionally doped (UID) β-Ga2O3 substrate grown by the vertical Bridgman method is evaluated by analyzing the performance uniformity of metal-oxide-semiconductor field-effect transistors as test structures fabricated on a Si-doped channel layer grown by metal-organic chemical vapor deposition. The high quality and homogeneity of the substrate material was confirmed by the uniform statistical distribution of device parameters across the wafer. Fabricated devices exhibited standard deviations of just 7.32 mA/mm for maximum current density, 3.92 V threshold voltage, and 0.88 mS/mm for peak transconductance, indicating a highly uniform epitaxial layer and channel. Mitigation of the silicon (Si) peak at the substrate-epitaxy interface was highly effective, removing the peak in 99% of devices that were tested via capacitance-voltage testing. The high yield and consistent electrical characteristics validate that the vertical Bridgman substrate technology produces a mature and uniform material platform suitable for scaling up β-Ga2O3 power electronics.

  PublisherDOI

• Lateral GaN Schottky superjunction diodes with buried p-GaN by NH3-MBE

  APL Electronic Devices · 2026-04-22

  articleOpen access

  In this work, we demonstrate lateral GaN Schottky superjunction diodes using a p–n–p layer structure. The lateral nature of these devices circumvents the difficulties in achieving charge balance with etch and regrowth techniques. The p–n–p layer Schottky superjunction diodes are compared to reference lateral Schottky diodes on n-GaN to demonstrate the effect of net dopant balance in reverse bias, which resulted in an ∼80× improvement in breakdown voltage with the charge balanced layers with no degradation in the forward on-state characteristics.

  PublisherDOI

• Orientation-dependent <i>β</i>-Ga2O3 heterojunction diode with atomic layer deposition (ALD) NiO

  Applied Physics Letters · 2025-09-22 · 3 citations

  articleSenior author

  This work reports the demonstration of ALD-deposited NiO/β-Ga2O3 heterojunction diodes (HJDs) on low doped (ND-NA ≤ 1 × 1016 cm−3) drift layers and highly doped (001) &amp; (100) n+ substrates (ND-NA &amp;gt; 1 × 1018 cm−3) with experimental observation of a parallel-plane junction electric field as high as 7.5 MV/cm, revealing a crystal orientation dependence in β-Ga2O3. We use a metalorganic precursor, bis(1,4-di-tert-butyl-1,3-diazadienyl) (nickel Ni(tBu2DAD)2), with ozone (O3) to deposit NiO. The NiO/β-Ga2O3 HJD on the 7.7 μm-thick HVPE-grown drift region exhibited an on-state current density of ∼20 A/cm2 at 5 V, ∼10−8 A/cm2 reverse leakage at low reverse bias (−5 V), and a rectifying ratio (Jon/Joff) of ∼109. The HJD broke down at ∼2.2 kV reverse bias, corresponding to a ∼3.4 MV/cm parallel-plane junction electric field, with a noise-floor reverse leakage (10−8–10−6 A/cm2, nA) at 80% of the device's catastrophic breakdown voltage. The NiO/β-Ga2O3 HJDs on n+ (001) &amp; (100) highly doped substrates exhibited breakdown voltages at 12.5–16.0 and 28.5–70.5 V, respectively, with extracted critical electric fields (EC) at 2.30–2.76 and 4.33–7.50 MV/cm, revealing a substrate crystal orientation dependence on breakdown electric field for β-Ga2O3. The 7.5 MV/cm EC reported here is one of the highest parallel-plane junction electric fields reported in literature.

  PublisherDOI

• Multi-fin β -Ga 2 O 3 Vertical FinFET with Interfin Field Oxide Exhibiting a Breakdown Voltage of 1.8kV and Power Figure of Merit of 1GW/cm 2

  2025-06-25

  preprintOpen accessSenior author

  We present a novel multi-fin, normally-off vertical FinFET based on β-Ga 2 O 3 , incorporating an inter-fin field oxide layer to enhance the breakdown voltage. Narrow fins with a width of 200 nm were fabricated using electron beam lithography, enabling enhancement-mode operation with a positive threshold voltage of 1.8 V. A thick dielectric layer was deposited at the bottom of the inter-fin trenches, serving as a field oxide, which increased the breakdown voltage to 1.8 kV-more than double the 800 V observed in devices without the field oxide. The device demonstrates a specific on-resistance of 3.2 mΩ-cm 2 and supports a maximum current density of 1.2 kA/cm 2. These characteristics yield a record-high power figure of merit of 1.01 GW/cm 2 for any multi-fin β-Ga 2 O 3-based vertical transistor.

  PublisherOA PDFDOI

• AI and Machine Learning in Urology: Current Uses and Future Directions

  2025-03-31

  book-chapterSenior author

  Background: Artificial Intelligence (AI) and Machine Learning (ML) have significantly transformed modern urology by enhancing diagnostic accuracy, surgical precision, and patient management. AI-driven innovations are increasingly integrated into urological practice, enabling early disease detection, predictive analytics, risk stratification, and robotic-assisted surgeries. This paper explores the current landscape of AI in urology, analyzing its applications in diagnostics, treatment planning, and surgical interventions. It highlights AI-driven technologies' benefits, challenges, and future research directions in optimizing patient care. Methods: A comprehensive literature review was conducted on AI applications in urology, examining studies on machine learning models—including deep learning and reinforcement learning—for detecting prostate, kidney, and bladder cancer, predictive analytics for disease progression, and AI-enhanced robotic surgeries. The analysis encompasses regulatory considerations, ethical implications (including data bias and patient privacy concerns), and real-world applications of AI in clinical settings. Results: AI performs superiorly in diagnostic imaging, histopathological analysis, and personalized treatment recommendations. Machine learning models enhance risk stratification, enabling more targeted therapeutic approaches. AI-driven robotic surgical systems enhance precision and reduce complications, while AI-powered remote monitoring tools optimize postoperative care. However, data bias, interpretability, regulatory constraints, and ethical concerns hinder widespread adoption. Conclusion: AI is revolutionizing urology by improving efficiency, accuracy, and patient outcomes. Future advancements in AI-driven precision medicine, autonomous robotic surgery, and AI-integrated telemedicine are promising. Addressing challenges related to data privacy, bias mitigation, and regulatory approval will be crucial for the seamless integration of AI into urological practice. Continued research and interdisciplinary collaboration will enhance AI's role in transforming urological healthcare.

  PublisherDOI

• Kilovolt-Class $β-Ga_2O_3$ Field-Plated Schottky Barrier Diodes with MOCVD-Grown Intentionally $10^{15}$ $cm^{-3}$ Doped Drift Layers

  ArXiv.org · 2025-09-17

  preprintOpen accessSenior author

  We report on the growth optimization of intentionally low-doped ($10^{15}$ $cm^{-3}$) high-quality $β-Ga_2O_3$ drift layers up to 10 $μm$ thick via MOCVD and the fabrication of kilovolt-class field plated Schottky barrier diodes on these thick drift layers. Homoepitaxial growth was performed on (010) $10^{15}$ $cm^{-3}$ substrates using TMGa as the Ga precursor. Growth parameters were systematically optimized to determine the best conditions for high quality thick growths with the given reactor geometry. Chamber pressure was found to improve the growth rate, mobility, and roughness of the samples. Growth rates of up to 7.2 $μm$/hr., thicknesses of up to 10 $μm$, Hall mobilities of up to 176 $cm^2$/Vs, RMS roughness down to 5.45 nm, UID concentrations as low as $2 \times$ $10^{15}$ $cm^{-3}$, and controllable intentional doping down to $3 \times$ $10^{15}$ $cm^{-3}$ were achieved. Field plated Schottky barrier diodes (FP-SBDs) were fabricated on a $6.5 \times$ $10^{15}$ $cm^{-3}$ intentionally doped 10 $μm$ thick film to determine the electrical performance of the MOCVD-grown material. The FP-SBD was found to have current density $&gt;$100 A/$cm^2$ at 3 V forward bias with a specific differential on resistance ($R_{on,sp}$) of 16.22 m$Ω$.$cm^2$ and a turn on voltage of 1 V. The diodes were found to have high quality anode metal/semiconductor interfaces with an ideality factor of 1.04, close to unity. Diodes had a maximum breakdown voltage of 1.50 kV, leading to a punch-through maximum field of 2.04 MV/cm under the anode metal, which is a state-of-the-art result for SBDs on MOCVD-grown (010) drift layers.

  PublisherOA PDFDOI

• Digital Twin-Enabled Real-Time Optimization System for Traffic and Power Grid Management in 6G-Driven Smart Cities

  IEEE Internet of Things Journal · 2025-04-29 · 10 citations

  article

  The advent of 6G-enabled Internet of Everything(IoE) technologies is set to revolutionize urban infrastructures by providing fast, consistent, and low-delay capabilities for communication. 6G connectivity will integrate traffic and power grids for adaptive urban management. However, current traffic networks and power grids face critical challenges such as fragmented data processing, delayed responses, and outdated resource management leading to inefficiencies like traffic congestion and power outages. In 6G-enabled smart grid cities, system complexity and interdependence demand dynamic, real-time solutions, further exacerbating inefficiencies. To address these issues, this study introduces Digital Twin-enabled Real-time Optimization System (DT-ROS), a dynamic framework designed to optimize urban traffic and power grid systems. DT-ROS integrates a dual-tier Digital Twin (DT) and an advanced scheduling framework based on Priority Age of Information Deep Q Scheduler (PAoI-QS). The dual-tier framework builds an elementary and Integrated Digital Twin (IDT) with Auto-Regressive Integrated Moving Average (ARIMA)-based forecasting for accurate real-time traffic and energy demand predictions. The advanced scheduling framework minimizes the Age of Information (AoI), ensuring decision-making relies on the most current and relevant data. By continuously monitoring and processing real-time data, DT-ROS creates virtual models to simulate system behavior and dynamically allocate resources. Simulation results demonstrate the effectiveness of DT-ROS, achieving a 30% reduction in traffic congestion and a 25% improvement in power grid stability compared to existing methods. To create effective, robust, and sustainable urban systems for future smart cities, DT-ROS addresses traffic and electricity problems.

  PublisherDOI

• QuaRTA-6G: Unified Post-Quantum Security and Quantum Learning for UAVs in 6G IoT

  IEEE Internet of Things Journal · 2025-11-11

  article

  Unmanned Aerial Vehicles (UAVs), as key enablers of 6G-enabled Internet of Things (IoT) ecosystems, facilitate dynamic aerial coverage, seamless edge intelligence, and adaptive routing. However, despite these advantages, the reliability and trustworthiness of UAV swarms in 6G remain critical concerns due to rising quantum threats and limitations of traditional machine learning approaches. The paper presents QuaRTA-6G, a Quantum-Resilient, Trust-aware, and Accountable framework that provides a unified solution for 6G UAV swarms. QuaRTA-6G achieves security, trust, and efficiency by seamlessly combining post-quantum cryptography for secure communication, a decentralized ledger for identity and trust management, and Variational Quantum Federated Learning (VQFL) for efficient swarm intelligence. For quantum-resistant authentication and immutable UAV identity verification, QuaRTA-6G leverages CRYSTALS-Kyber with blockchain. Through simulations, QuaRTA-6G achieves secure authentication handshakes in under 2 ms and scales robustly to swarms of more than 100 UAVs, keeping high integrity even under 20% packet loss. Experiments demonstrate that, even under strong data poisoning attacks, the framework achieves 92% accuracy and 85% mission success rate, while comprehensive resource analysis confirms its feasibility across both standard and resource-constrained UAV platforms. Furthermore, an ablation study demonstrates that each module of QuaRTA-6G is essential for ensuring a responsible and trustworthy 6G UAV framework.

  PublisherDOI

• Nutcracker Syndrome: Anatomical, Physiological and Clinical Correlations

  2025-02-08

  book-chapter1st authorCorresponding

  Nutcracker Syndrome (NCS) is a chronic vascular condition that occurs when the left renal vein (LRV) becomes compressed between nearby anatomical structures. This compression disrupts blood flow to the kidneys, leading to increased pressure within the kidney. Patients may experience a variety of symptoms, including hematuria (blood in urine), flank or abdominal pain, orthostatic proteinuria (protein in urine while standing), varicocele in men, or pelvic congestion syndrome in women. Prolonged elevated venous pressure can cause ongoing pain in the flank, pelvis, or lower back, especially during activities that increase intra-abdominal pressure. Over time, this chronic hypertension places significant stress on both the heart and kidneys, potentially leading to cardiovascular complications and worsening kidney function. Nutcracker syndrome is diagnosed through Doppler ultrasound, CT, MRI, and venography to assess renal vein compression. Treatment options include conservative management for mild cases, endovascular stenting, or surgical procedures like renal vein transposition and autotransplantation for severe cases. Timely diagnosis ensures effective management, relieving symptoms and preventing complications.

  PublisherDOI

• Evidence for Ga clusters in β-Ga2O3 from Raman spectroscopy and density functional theory

  Journal of Applied Physics · 2025-10-03

  articleOpen access

  Monoclinic gallium oxide (β-Ga2O3) single crystals have a Raman mode at ∼250 cm−1 that is strongly correlated with free-electron density. Prior work attributed this peak to an electronic excitation of a shallow donor impurity band. However, heavily n-type thin films grown by metalorganic chemical vapor deposition or molecular beam epitaxy do not have the peak. In the present work, an alternate model is proposed: the 250 cm−1 Raman peak arises from Ga clusters, defined as two or more Ga atoms that form Ga–Ga bonds. Raman mapping reveals variations in the frequency that are consistent with a distribution of cluster sizes. The intensity of the peak decreases as the temperature is raised, attributed to melting of the Ga clusters. First-principles calculations indicate that the 250 cm−1 mode is due to Ga–Ga bond-stretching vibrations. As the Fermi energy is raised, the formation of Ga–Ga dimers becomes energetically favorable, explaining the correlation between n-type conductivity and the appearance of the Raman peak.

  PublisherOA PDFDOI

Recent grants

• EAGER: Collaborative Research: Epitaxial Stabilization of Polar Epsilon-phase Gallium Oxide Thin Films

  NSF · $85k · 2019–2021

Frequent coauthors

• Siddharth Rajan

  123 shared

• P. Sadayappan

  University of Utah

  102 shared

• Priyanka Ghosh

  97 shared

• Arkka Bhattacharyya

  University of Utah

  94 shared

• Janet Jansson

  Pacific Northwest National Laboratory

  89 shared

• Ruonan Wu

  Pacific Northwest National Laboratory

  89 shared

• Madison Blumer

  Pacific Northwest National Laboratory

  89 shared

• Jason McDermott

  Pacific Northwest National Laboratory

  89 shared