Transient characteristics of β-Ga2O3 nanomembrane Schottky barrier diodes on various substrates

At a Glance

Metadata	Details
Publication Date	2022-07-07
Journal	Journal of Physics D Applied Physics
Authors	Junyu Lai, Jung‐Hun Seo
Institutions	University at Buffalo, State University of New York
Citations	3
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-k Diamond Substrates for $\beta$-Ga${2}$O${3}$ Power Devices

Executive Summary

This research highlights the critical role of high-thermal-conductivity (high-k) substrates, specifically diamond, in optimizing the transient electrical performance and thermal management of $\beta$-Ga${2}$O${3}$ Nanomembrane Schottky Barrier Diodes (SBDs).

Core Finding: $\beta$-Ga${2}$O${3}$ SBDs transfer-printed onto diamond substrates exhibited the shortest transient rise and fall times (as low as 1.07 µs at 20 °C), demonstrating superior heat dissipation compared to Si, Sapphire, and Polyimide.
Thermal Imperative: Due to the inherently low thermal conductivity of $\beta$-Ga${2}$O${3}$ (10-25 W/m·K), integrating it with high-k diamond (2200 W/m·K) is essential to mitigate self-heating effects and ensure device reliability at high power.
Thickness Dependence: The study systematically investigated $\beta$-Ga${2}$O${3}$ NM thicknesses (300 nm, 600 nm, 1000 nm), confirming that thinner NMs on high-k substrates dissipate heat faster, preventing device overheating.
Material Validation: Diamond provides a thermal conductivity 15 times greater than Si (144 W/m·K) and 55 times greater than Sapphire (40 W/m·K), validating its necessity for next-generation wide-bandgap thermal management.
Fabrication Complexity: The devices required precise micro-transfer printing and advanced metalization stacks (Ti/Pt/Au Schottky contact) to achieve functional SBDs, demanding high-precision material sourcing.

Technical Specifications

The following hard data points were extracted from the research paper, focusing on material properties and device performance metrics.

Parameter	Value	Unit	Context
Substrate Thermal Conductivity (Diamond)	2200	W/m·K	Highest performing substrate tested
Substrate Thermal Conductivity (Si)	144	W/m·K	Reference semiconductor substrate
Substrate Thermal Conductivity (Sapphire)	40	W/m·K	Reference dielectric substrate
$\beta$-Ga${2}$O${3}$ NM Thickness Range	300, 600, 1000	nm	Nanomembrane dimensions tested
$\beta$-Ga${2}$O${3}$ NM Thermal Conductivity (100 nm)	3.1	W/m·K	Decreases with thickness
$\beta$-Ga${2}$O${3}$ NM Thermal Conductivity (1000 nm)	8.68	W/m·K	Increases with thickness
Shortest Transient Time (Diamond, 300 nm, 20 °C)	1.07	µs	Optimal rise and fall time
Longest Transient Time (PI, 300 nm, 20 °C)	2.65 (Rise), 2.85 (Fall)	µs	Low-k substrate performance
Operating Temperature (Elevated)	70 (400)	°C (K)	Condition used to test thermal stability
Pulsed I-V Current Compliance	3	mA	Limit set to prevent thermal damage
Schottky Metal Stack	Ti/Pt/Au (20/30/100)	nm	Metalization recipe used
Ohmic Metal Stack	Ti/Au (20/100)	nm	Metalization recipe used
Time Resolution of Pulsed I-V System	0.17	µSec	Measurement system capability

Key Methodologies

The experiment relied on advanced material preparation and high-resolution electrical characterization techniques to isolate the thermal effects of the substrate.

Material Preparation: $\beta$-Ga${2}$O${3}$ bulk substrate (moderately Sn doped, 1x10¹⁸ cm^-3) was grown via Molecular Beam Epitaxy (MBE).
Nanomembrane Creation: $\beta$-Ga${2}$O${3}$ Nanomembranes (NMs) of varying thicknesses (300 nm, 600 nm, 1000 nm) were created using mechanical exfoliation.
Micro-Transfer Printing: NMs were carefully transfer-printed onto four distinct substrates (Diamond, Si, Sapphire, and Polyimide/SU-8) using a Polydimethylsiloxane (PDMS) elastomeric stamp.
Ohmic Contact Optimization: A BCl₃/Ar plasma treatment via Reactive Ion Etcher (RIE) was performed on the $\beta$-Ga${2}$O${3}$ NMs prior to metal deposition to achieve Ohmic contact without requiring high-temperature annealing.
Metalization: Ohmic (Ti/Au) and Schottky (Ti/Pt/Au) metal stacks were deposited to complete the SBD fabrication.
Transient Characterization: Devices were measured using a sub-micron second resolution time-resolved pulsed I-V system (Keithley 4200 SCS) under both room temperature (20 °C) and elevated temperature (70 °C) conditions.
Thermal Simulation: Multiphysics simulation (COMSOL) was used to model temperature profiles and verify the relationship between NM thickness, substrate thermal conductivity, and heat dissipation capacity.

6CCVD Solutions & Capabilities

The research conclusively demonstrates that diamond is the optimal substrate for maximizing the performance and reliability of $\beta$-Ga${2}$O${3}$ power devices. 6CCVD is uniquely positioned to supply the high-quality diamond materials and customization services required to replicate and advance this research.

Applicable Materials

To replicate or extend this high-performance thermal management research, engineers require high-purity, high-thermal-conductivity diamond substrates.

6CCVD Material Recommendation	Specification	Application Context
Thermal Grade Single Crystal Diamond (SCD)	TC: > 2000 W/m·K, Polishing: Ra < 1 nm	Ideal for direct integration with $\beta$-Ga${2}$O${3}$ NMs where maximum heat spreading and surface quality are paramount.
High-Purity Polycrystalline Diamond (PCD)	TC: > 1800 W/m·K, Plates up to 125 mm	Cost-effective solution for large-area $\beta$-Ga${2}$O${3}$ device arrays requiring excellent thermal management across inch-sized wafers.
Custom Substrates	Thickness up to 10 mm	Providing robust, thick diamond heat sinks for high-power modules, ensuring structural integrity and long-term thermal stability.

Customization Potential

The fabrication process detailed in the paper requires precise control over material dimensions and interfacial layers, capabilities that are standard offerings at 6CCVD.

Custom Metalization Stacks: The paper utilized specific Ti/Pt/Au Schottky contacts. 6CCVD offers internal metalization capabilities, including Au, Pt, Pd, Ti, W, and Cu, allowing researchers to precisely replicate the required Ti/Pt/Au (20/30/100 nm) stack or test alternative thermal boundary conductance (TBC) layers.
Precision Polishing: Achieving reliable transfer printing and low thermal resistance interfaces requires ultra-smooth surfaces. 6CCVD guarantees Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD, ensuring optimal thermal and electrical contact for $\beta$-Ga${2}$O${3}$ NMs.
Custom Dimensions: 6CCVD can supply custom diamond plates and wafers up to 125 mm (PCD), supporting scaling efforts for high-frequency and high-power $\beta$-Ga${2}$O${3}$ applications.

Engineering Support

6CCVD’s in-house PhD engineering team specializes in wide-bandgap semiconductor integration and thermal management. We offer expert consultation to assist researchers in optimizing their $\beta$-Ga${2}$O${3}$ projects.

Thermal Interface Optimization: We provide guidance on selecting the optimal diamond grade and surface preparation techniques to minimize thermal boundary resistance (TBR) between the $\beta$-Ga${2}$O${3}$ layer and the diamond heat sink.
Material Selection for High-Power Applications: Assistance in choosing between SCD and PCD based on cost, size, and specific thermal requirements for similar $\beta$-Ga${2}$O${3}$ SBD projects.
Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive, high-value diamond substrates directly to your research facility.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Abstract In this paper, transient delayed rise and fall times for beta gallium oxide ( β -Ga 2 O 3 ) nanomembrane (NM) Schottky barrier diodes (SBDs) formed on four different substrates (diamond, Si, sapphire, and polyimide) were measured using a sub-micron second resolution time-resolved electrical measurement system under different temperature conditions. The devices exhibited noticeably less-delayed turn on/turn off transient time when β -Ga 2 O 3 NM SBDs were built on a high thermal conductive (high- k ) substrate. Furthermore, a relationship between the β -Ga 2 O 3 NM thicknesses under different temperature conditions and their transient characteristics were systematically investigated and verified it using a multiphysics simulator. Overall, our results revealed the impact of various substrates with different thermal properties and different β -Ga 2 O 3 NM thicknesses on the performance of β -Ga 2 O 3 NM-based devices. Thus, the high- k substrate integration strategy will help design future β -Ga 2 O 3 -based devices by maximizing heat dissipation from the β -Ga 2 O 3 layer.

Tech Support

Original Source

DOI: https://doi.org/10.1088/1361-6463/ac7f67

References

2020 - Field-plated lateral Ga2O3 MOSFETs with polymer passivation and 8.03 kV breakdown voltage [Crossref]
2018 - A review of Ga2O3 materials, processing, and devices [Crossref]
2012 - Gallium oxide (Ga2O3 metal-semiconductor field-effect transistors on single-crystal β-Ga2O3 (010) substrates [Crossref]
2019 - A field-plated Ga2O3 MOSFET with near 2-kV breakdown voltage and 520 mΩ·cm2 on-resistance [Crossref]
2017 - β-Ga2O3 MOSFETs for radio frequency operation [Crossref]
2018 - High responsivity β-Ga2O3 metal-semiconductor-metal solar-blind photodetectors with ultraviolet transparent graphene electrodes [Crossref]
2020 - Investigation of thermal properties of β-Ga2O3 nanomembranes on diamond heterostructure using Raman thermometry [Crossref]
2015 - Anisotropic thermal conductivity in single crystal β-gallium oxide [Crossref]
1979 - Thermal conductivity and electrical properties of 6H silicon carbide [Crossref]