Wide Bandgap Devices

Wide Bandgap devices like Silicon Carbide SiC and Gallium Nitride GaN are the future of power electronics. They enable ultra high efficiency converters for electric vehicle drivetrains and fast chargers.

Core Concept

The bandgap energy of SiC is 3.2 eV compared to 1.1 eV for standard Silicon. This higher energy requirement to break electron bonds gives these materials superior thermal and electrical properties.

A higher critical breakdown field allows the drift region to be much thinner. This drastically reduces the on state resistance Rds on even for 1200V rated SiC MOSFETs.

GaN HEMTs exhibit zero reverse recovery charge. This allows switching frequencies to exceed 1 MHz reducing the size of passive magnetic components dramatically.

Key Formulas

Higher switching frequency fsw reduces the required inductor size. L is inversely proportional to fsw.

Given: Silicon fsw = 20 kHz, SiC fsw = 200 kHz, L_silicon = 1 mH
Formula: L_sic = L_silicon * (fsw_silicon / fsw_sic)
Steps: L_sic = 1e-3 * (20 / 200)
Final Answer: 0.1 mH

Exam Tip: While GaN is superior for ultra fast switching at voltages under 600V SiC dominates the high power high voltage space above 1200V.

Performance Parameters

• SiC Bandgap: 3.2 eV
• Thermal conductivity: 3 times better than Silicon
• Operating temperature: up to 200 C
• GaN switching speed: up to 10 MHz
• Breakdown field: 10 times higher than Silicon

Quick Revision

• Thinner drift regions lower Rds on
• Higher junction temperatures allowed
• Smaller passive components due to high frequency
• Zero reverse recovery in GaN
• Premium cost limits widespread adoption
• Exam trap: Thinking GaN devices are heavily used for 3300V traction