Gallium Nitride (GaN) is among the most advanced technologies in power electronics. It allows the development of powerful devices with increased power density, reduced ON resistance, and very high-frequency switching.  For the same current and voltage rating, the GaN-based devices offer a substantial reduction in the chip size as compared to the conventional silicon-based power devices, thus reducing the power converter’s global volume. Furthermore, the reduction in switching power losses provides an increasingly effective solution for converter applications featuring emerging opportunities for the expanding power electronics market. The increasing advancement in GaN devices is benefitting several areas of power electronics, especially the low-voltage (< 200 V) power applications, such as telecom/datacom, server SMPS, and wireless charging. It is also used in power converters, electric vehicles (EVs), industrial automation, and modular battery management systems (BMS). The GaN market is experiencing continuous growth in consumer electronics applications. According to Cognitive Market Research, the global GaN Power Device market size will be USD 3.06 billion in 2024 and will expand at a compound annual growth rate (CAGR) of 26.3% from 2024 to 2031. This article discusses the features of GaN for power applications and the various devices in which GaN is used.

Features of GaN for Power Applications

• Wide Bandgap Energy: GaN has a bandgap of 3.4 eV, which is much wider than silicon’s 1.1 eV. Bandgap is the energy required to move electrons from the valence band to the conduction band. The wider bandgap allows GaN devices to withstand higher electric fields without breaking down, thus enabling them to handle higher voltages (up to 1200 V and beyond). Also, due to the large bandgap the GaN devices can operate at higher temperatures (up to 300^oC) as compared to Silicon (which operates around 150^oC).
• High Electron Mobility: GaN has significantly higher electron mobility as compared to silicon or any other material like GaAs. Electron mobility is the ability of an electron to move through a semiconductor when an electric field is applied. The high electron mobility enables faster switching speeds of transistors which is a crucial parameter in power electronics. Also, faster switching speeds reduce the time that the transistor spends in a partially conducting state, thus minimizing the switching losses.
• High Power Density: Power Density is the amount of power that can be delivered or handled per unit volume of the semiconductor. GaN can handle more power in small packages as compared to silicon, thus making it possible to design smaller power systems that are highly efficient. This is important in space-constrained applications like electric vehicle (EV) inverters, onboard chargers, and consumer electronics. Also, due to high power density, it offers lower conduction losses and thus supports higher currents with lower resistance implying more efficiency.
• High Breakdown Electric Field: Breakdown voltage is the maximum voltage that the material can withstand before undergoing electrical breakdown. GaN has a high breakdown voltage (3 MV/cm) which allows the devices to operate at higher voltages without degradation or failure. This parameter is crucial for high-voltage power systems such as those found in grid infrastructure, renewable energy systems (solar inverters), and in industrial applications where high-voltage power conversion is necessary.
• Thermal Conductivity: Thermal conductivity is the measure of how well a material can conduct heat. GaN has moderate thermal conductivity (1.3 W/cm K) which when combined with its high efficiency and ability to operate at high temperatures allows for better thermal management in high power applications.

These features make it possible to use GaN-based devices in high-power applications like electric vehicles, renewable energy systems, data centers, industrial motor drives, etc. It offers significant advantages over traditional silicon technology, thus enabling more compact, efficient, and reliable power systems. 

Examples of GaN in Power Electronics

GaN for DC-DC Power Converters

The DC-DC power converter is used in almost all industrial and domestic electronic equipment such as consoles, laptops, computers, servers, storage systems, etc. DC-DC converter in the form of a power brick that complies with the standard sizes and footprints settled by the Distributed-Power Open System Alliance (DOSA) is the solution for a flexible modular power supply. The advantage of using the power brick is that the equipment design engineers do not need to be experts in power supply design, the power brick can be mounted internally or externally on the PCB. It consists of the switching topology (a synchronous buck or boost topology) and a controller.

The power density per unit area is a crucial challenge for the brick arrangement. HEMT devices are an excellent choice for compact and high-efficiency modular power supply systems. The low-voltage GaN FETs have a compact footprint with an excellent Figure of Merit (FOM). The size and shape of the magnetic components can be improved by increasing the switching frequency which is achievable by GaN FETs. Also, the GaN-based HEMT devices reduce the dead time in the implementation of a synchronous buck converter. 

The table given below shows the advantages of using GaN HEMT (High Electron Mobility Transistor) (GS61004B from GaN System in GaNPX packaging) instead of MOSFET (ISZ230N10NM6 from Infineon in a PG-TSDSON-8FL package) for power brick applications in terms of the main electrical parameters.

 The LLC resonant converter is one of the topologies in which the use of e-mode GaN FETs helps in achieving the best power density. The zero-voltage switching achieved in an LLC converter increases the efficiency, and the high switching frequency (1 to 10s of MHz). LLC is one of the widely used converter topologies for inductive wireless power transfer (WPT) systems. The compact size of the HEMTs is a crucial factor for wireless charging applications.

GaN for Motor Drive Applications

In recent years, GaN FETs for low voltages are also used in applications for inverter drives for brushless direct current (BLDC) and AC motors (mostly for voltages < 200 V) due to the possibility of reaching high switching frequencies (> 100 kHz) and thus reducing the overall dimensions of the inverter. This allows the integration of the motor, inverter, and control in a single compact system obtaining an efficient and integrated modular motor drive. The switching frequency for a MOSFET-based inverter is equal to or below 40 kHz, and the dead time with MOSFET switching legs is maintained from 200 ns to 500 ns. The dead-time length impacts the generation of a six harmonic on the electrical frequency of the generated torque which in turn influences the motor efficiency performance, thus increasing the mechanical vibration and the winding temperature. On the other hand, the dead time in GaN FETs can be reduced to tens of nanoseconds, thus improving the quality of the waveform and drastically decreasing the sixth harmonic effect.  GaN FET inverter easily reaches 100 kHz of switching frequency. Also, by increasing the PWM (Pulse Width Modulation) frequency, the ripples in the current are reduced.

GaN for LIDAR Applications

The Light Detection and Ranging (LIDAR) technology identifies the distance to an object by illuminating it with laser light. It is used as a remote recognition device for developing self-driving vehicles and ADAS (Advanced Driver Assistance Systems). There are two modes of operation of LIDAR: direct time of flight (DToF) and indirect time of flight (IToF). The first LIDAR form sends individual pulses and measures the time of reflection to calculate the distances, whereas the second method compares the phase of the transmitted and reflected signal pulse to calculate the distance of the target. In recent years, the IToF solution has become dominant due to its versatility, simple design, and low cost. It is applied mainly in the medium range of distance (from 1 m to 10 m) and is primarily used in robotics, UAVs, and autonomous vehicles. The diagrammatic representation of the operation of the IToF method is shown in the figure below.

The laser used in LIDAR requires a specific pulse current for operation in the IToF system. The current pulse must be obtained through a low-voltage circuit that is based on a switch that is capable of quickly managing high currents. The GaN FET is an excellent candidate for this kind of application. EPC has developed an integrated power stage and driver circuit with a voltage switching time of 750 ps at a typical voltage supply of 30 V with 15 A of the peak current and an operative frequency up to 200 MHz that is suitable for LIDAR operation. The most widely used circuit to generate the pulse current is shown in the figure below, and the power and the control stage IC is also presented below.

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