Power Semiconductors

Description

Gallium Nitride (GaN) is a third-generation semiconductor material (wide bandgap semiconductor). Compared with traditional silicon (Si) and silicon carbide (SiC), it has advantages such as higher electron mobility, higher withstand voltage, and higher switching frequency, and is widely used in high-efficiency power electronic systems.

1. Core characteristics of GaN

2. Types of GaN power devices

(1) GaN HEMT (High electron Mobility Transistor)

l Structure: Based on the AlGaN/GaN heterojunction, a 2DEG (two-dimensional electron gas) is formed to achieve extremely high electron mobility.

l Features:

¢ Ultra-low on-resistance (R DS(on)).

¢ Ultra-fast switching speed (MHz level).

l Applications: High-frequency power supply (fast charge, RF), LiDAR.

(2) GaN FET (Field-Effect Transistor)

l Enhanced (E-mode) : normally off, safe and easy to drive.

l Depletion mode (D-mode) : Normally open, requires negative voltage to turn off (with driver IC).

(3) GaN power IC

l Integrated solution: Integrate GaN FET, driver, and protection circuits.

l Advantages: Simplified design and improved reliability (e.g. For server power supply).

3. The core advantage of GaN

(1) Ultra-high switching frequency (MHz level)

l Traditional Si MOSFET: usually <500kHz.

l GaN devices: Up to 10MHz+, significantly reducing inductor/capacitor volume.

l Applications:

¢ Fast charge your phone (such as USB PD 3.1 140W).

¢ Ultra-thin power adapter (such as fruit 30W GaN charger).

(2) Low conduction loss

l More than 50% lower than Si MOSFETs of the same specification, improving energy efficiency (e.g. Data center power efficiency >96%).

(3) High-temperature performance

l Working temperature up to 200°C+ (Si generally <150°C), suitable for harsh environments.

(4) Miniaturization

l GaN devices are 50% to 70% smaller than Si at the same power.

4. Typical applications of GaN

5. GaN vs SiC vs Si comparison

6. The challenge of GaN

1. High cost: GaN wafers are currently more expensive than Si, but they are gradually decreasing as mass production begins.

2. Reliability verification: Long-term stability (such as dynamic R DS(on)) needs to be further optimized.

3. Complex drive design: Some GaN devices require special drive circuits (such as negative turn-off).

7. Future trends

1. Higher voltage levels: Developing 1200V GaN devices, moving into main inverters for electric vehicles.

2. Integration: More GaN ics (integrated driver + protection) to lower the design threshold.

3. 8-inch wafer mass production: Cost reduction (currently mainstream 6-inch).

4. Complementary with SiC:

¢ GaN: High frequency, medium low voltage (<900V) scenarios (fast charging, communication).

¢ SiC: High voltage, high temperature scenarios (electric vehicles, photovoltaics).

8. Summary

l GaN advantages: High frequency, high efficiency, miniaturization, suitable for fast charging, 5G, data centers and other scenarios.

l Applicable voltage: Currently, it is mainly under 650V, gradually moving towards 1200V.

l Future: As costs fall, GaN will gradually replace mid - and low-voltage Si MOSFETs and part of the SiC market.

Sample application:

l Fruit 140W USB-C charger (GaN HEMT for ultra-high power density).

l Electric vehicles may use GaN for the next generation of OBC (on-board charger).