Technology and Applications of Wide Bandgap Semiconductor Materials - Current State and Future Trends

At a Glance

Metadata	Details
Publication Date	2023-09-18
Journal	Energies
Authors	Omar Sarwar Chaudhary, Mouloud Denaï, Shady S. Refaat, Georgios Pissanidis
Institutions	Texas A&M University at Qatar, University of Hertfordshire
Citations	56
Analysis	Full AI Review Included

Executive Summary

This review analyzes the current state and future trends of Wide Bandgap (WBG) semiconductor materials (Silicon Carbide, Gallium Nitride, and Diamond) as superior alternatives to Silicon (Si) in power electronics applications.

Core Value Proposition: WBG materials offer significantly higher breakdown voltage, faster switching speeds, lower switching losses (up to 98% reduction compared to Si), and superior thermal conductivity.
System Benefits: The ability to switch at higher frequencies allows for substantial reduction in the size, weight, and cost of passive components (inductors, capacitors, cooling systems), leading to higher power density converters.
Material Maturity: SiC is commercially mature for high-voltage applications (1.2 kV and above, e.g., traction inverters). GaN is preferred for low-voltage applications (up to 600 V) due to cost-effective GaN-on-Si epitaxy and high-speed switching.
Future Potential: Diamond (Dia) possesses the highest theoretical performance metrics (bandgap, thermal conductivity) but is currently the least mature in terms of large-scale, defect-free wafer fabrication and n-type doping.
Market Impact: The highest projected growth for WBG devices is in Electric Vehicles (EVs), where SiC adoption is expected to improve fuel efficiency by up to 15% and reduce power control unit size by 40%.
Key Challenges: Widespread adoption is hindered by high material manufacturing costs, crystalline defects (e.g., micropipes in SiC), lack of industry standardization, and the need for advanced packaging and thermal management solutions.

Technical Specifications

Parameter	Value	Unit	Context
Si Bandgap (E_g)	1.12	eV	Reference material (300 K)
4H-SiC Bandgap (E_g)	3.26	eV	Wide bandgap material (300 K)
GaN Bandgap (E_g)	3.39	eV	Wide bandgap material (300 K)
Diamond Bandgap (E_g)	5.47	eV	Ultra-wide bandgap material (300 K)
Si Critical Electric Field (E_crit)	0.25 x 10⁶	V/cm	Low breakdown voltage capability
Diamond Critical Electric Field (E_crit)	5.6 x 10⁶	V/cm	Highest known breakdown field
4H-SiC Thermal Conductivity (κ)	420	W/mK	High thermal dissipation capability
Diamond Thermal Conductivity (κ)	2000	W/mK	Highest known thermal conductivity
Si Electron Mobility (µ_n,max)	1400	cm²/Vs	Reference material
4H-SiC Electron Mobility (µ_n,max)	1000-1140	cm²/Vs	High carrier mobility
GaN Electron Mobility (µ_n,max)	1250	cm²/Vs	High carrier mobility
SiC Wafer Size (Current Standard)	150 (6 inch)	mm	Commercial production
SiC Wafer Defect Density (Recent)	up to 0.25	/cm²	Improved quality for 150 mm wafers
GaN PSU Efficiency	96.3	%	Achieved at 1 MHz switching frequency in data centers
SiC Inverter Efficiency (EV)	97.1 to 99.7	%	Range across various drive cycles (e.g., US06, EPA Highway)
SiC Loss Reduction (EV)	41 to 85	%	Reduction of losses compared to Si inverters
WBG Energy Savings (Consumer Electronics)	7670	GWh/year	Estimated annual savings in the U.S. from laptop/phone adapters

Key Methodologies

The development and commercialization of WBG devices rely on specialized material growth and fabrication techniques:

SiC Wafer Processing: Focus on improving crystal growth techniques to reduce defects (micropipes) and increase wafer size (currently 150 mm, with 200 mm under development) to lower manufacturing costs and increase yield.
GaN Heteroepitaxy: GaN epilayers are grown on foreign substrates (heteroepitaxy) such as Si, SiC, or Sapphire. GaN-on-Si is the most cost-effective method, facilitating the development of low-voltage devices (<600 V).
Diamond Growth Techniques: High-quality diamond wafers are developed using Chemical Vapor Deposition (CVD) methods:
- Hot Filament CVD (HF CVD).
- Microwave-Enhanced CVD (MWCVD).
- High-Pressure High-Temperature (HPHT) technique (yields small, high-quality wafers).
Diamond Doping: P-type doping is achieved relatively easily using Boron. N-type doping remains a major challenge due to the lack of an efficient charge donor, limiting the commercial viability of bipolar devices.
Device Architecture Development:
- SiC: Focus on Schottky diodes and MOSFETs (up to 1.7 kV) and thyristors (up to 6.5 kV).
- GaN: Focus on High Electron Mobility Transistors (HEMTs) and Gate Injection Transistors (GITs), leveraging the 2DEG (two-dimensional electron gas) for high mobility and fast switching.
Performance Evaluation: Utilization of advanced Figures of Merit (FOMs) beyond traditional metrics, such as Baliga’s High-Frequency FOM (BHFM = µE_c²) and thermal FOMs (QF1, QF2, QF3), to accurately compare WBG materials under high-frequency and high-temperature operating conditions.

Commercial Applications

WBG semiconductors are poised to revolutionize several high-impact sectors by enabling higher efficiency and compact designs:

Automotive (Electric Vehicles—EVs/HEVs):
- Traction Inverters: SiC MOSFETs (900 V to 1.2 kV) are used to reduce switching losses and enable lightweight heatsinks.
- On-Board Chargers (OBCs): SiC-based OBCs have demonstrated 95% efficiency and a 10x improvement in power density.
Motor Drives (Variable Frequency Drives—VFDs):
- WBG VFDs enable higher switching frequencies, reducing the size of passive components and lowering audible system noise.
- Potential to reduce global energy losses in industrial motors by 10% to 30%.
Data Centers:
- Uninterruptible Power Supplies (UPS): SiC-based UPS units offer half the losses and are 10% more compact than similarly rated Si systems.
- Power Supply Units (PSUs): GaN-based PSUs enable high-frequency operation (1 MHz) and high efficiency (96.3%), reducing transformer winding losses and heat.
Distributed Energy Resources (DERs):
- Solar PV Inverters: SiC inverters increase efficiency from 96% (Si) to 99%, reducing system-level costs and footprint.
- Wind Turbine Converters: WBG devices enable an absolute efficiency improvement of 4.6% in wind energy conversion systems.
Consumer Electronics (External Power Supplies—EPS):
- GaN HEMTs in laptop and mobile phone adapters increase efficiency by 3% to 9% and allow for a 10x reduction in adapter size and weight.

View Original Abstract

Silicon (Si)-based semiconductor devices have long dominated the power electronics industry and are used in almost every application involving power conversion. Examples of these include metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), gate turn-off (GTO), thyristors, and bipolar junction transistor (BJTs). However, for many applications, power device requirements such as higher blocking voltage capability, higher switching frequencies, lower switching losses, higher temperature withstand, higher power density in power converters, and enhanced efficiency and reliability have reached a stage where the present Si-based power devices cannot cope with the growing demand and would usually require large, costly cooling systems and output filters to meet the requirements of the application. Wide bandgap (WBG) power semiconductor materials such as silicon carbide (SiC), gallium nitride (GaN), and diamond (Dia) have recently emerged in the commercial market, with superior material properties that promise substantial performance improvements and are expected to gradually replace the traditional Si-based devices in various power electronics applications. WBG power devices can significantly improve the efficiency of power electronic converters by reducing losses and making power conversion devices smaller in size and weight. The aim of this paper is to highlight the technical and market potential of WBG semiconductors. A detailed short-term and long-term analysis is presented in terms of cost, energy impact, size, and efficiency improvement in various applications, including motor drives, automotive, data centers, aerospace, power systems, distributed energy systems, and consumer electronics. In addition, the paper highlights the benefits of WBG semiconductors in power conversion applications by considering the current and future market trends.

Tech Support

Original Source

DOI: https://doi.org/10.3390/en16186689

References

2014 - A Survey of Wide Bandgap Power Semiconductor Devices [Crossref]
2022 - An overview of lifetime management of power electronic converters [Crossref]
2002 - Silicon carbide benefits and advantages for power electronics circuits and systems [Crossref]
1990 - Potential impact of emerging semiconductor technologies on advanced power electronic systems [Crossref]