Is GaN reliable? Or should we ask the question?

Gallium nitride (GaN) field effect transistors (FETs) are rapidly gaining adoption, given their ability to increase efficiency and reduce the size of power supplies. But before investing in this technology, you may still be curious about whether GaN is reliable. I am surprised that no one is asking whether silicon is reliable. After all, new silicon products are still coming out, and power supply designers are concerned about the reliability of silicon power devices.

In fact, the GaN industry has invested a lot of energy and time in reliability.

The question about silicon reliability is phrased differently, such as “Has this been qualified?” Although GaN devices have also been qualified in silicon, power supply manufacturers are not confident that the reliability of GaN FETs can be ensured using silicon methods. This is a valid point, as not all silicon device tests are applicable to GaN, and traditional silicon qualification itself does not include stress testing for the actual switching conditions used in power supplies. The JEDEC JC-70 Wide Bandgap Power Electronics Conversion Semiconductor Committee has published several GaN-specific guidelines to address these deficiencies.

Understanding GaN product reliability

Read the technical white paper “Achieving Lifetime Reliability of GaN Products” to learn more about our GaN reliability testing.

How to verify the reliability of GaN?

The reliability of GaN FETs can be verified through established silicon methods combined with reliability procedures and test methods. These reliability procedures and test methods are designed to address GaN-specific failure modes, such as the increase in dynamic drain-source on-resistance (RDS(ON)). Figure 1 lists the steps to achieve GaN product reliability.

Figure 1: GaN-specific reliability guidelines combined with established silicon standards

We divide testing into component-level and power-level modules, each with associated standards and guidelines. At the component level, TI performs bias, temperature and humidity stress tests based on traditional silicon standards, uses GaN-specific test methods, and determines lifetime by applying accelerated stress until device failure. At the power level, devices are operated under the stringent operating conditions of the relevant application. TI also verifies the robustness of devices under extreme operating conditions in occasional events.

GaN FET Reliability in Applications

The JEDEC JEP180 guidelines provide a common approach to ensure the reliability of GaN products in power conversion applications. To meet the requirements of JEP180, GaN manufacturers must demonstrate that their products have the required switching life under relevant stresses and operate in a reliable manner under the stringent operating conditions of the power supply. The former demonstration uses the Switching Accelerated Life Test (SALT) to stress the device, while the latter uses the Dynamic High Temperature Operating Life (DHTOL) test.

Devices are also subject to extreme operating conditions in the real world, such as short circuits and power line surges. TI GaN products such as the LMG3522R030-Q1 have built-in short-circuit protection. To achieve surge robustness in a range of applications, both hard-switching and soft-switching stresses need to be considered. GaN FETs handle power line surges differently than silicon FETs. Due to their overvoltage capability, GaN FETs do not go into avalanche breakdown, but instead switch through the surge. Having overvoltage capability also improves system reliability because avalanche FETs cannot absorb much of the avalanche energy, so the protection circuitry must absorb most of the surge. As surge absorption components degrade with age, they can subject silicon FETs to higher levels of avalanche, potentially leading to failure. In contrast, GaN FETs will continue to switch.

Are TI's GaN products reliable?

TI characterizes its GaN products according to the methodology shown in Figure 1. Figure 2 summarizes the results, showing results from both the component-level and power-level modules.

Figure 2: Using the methodology shown in Figure 1, the reliability of GaN FETs was verified with GaN-specific guidelines.

At the component level, TI GaN has passed traditional silicon qualification and has high reliability against GaN-specific failure mechanisms. TI designs and verifies its GaN products for high reliability against time-dependent breakdown (TDB), charge trapping and hot electron loss failure mechanisms, and demonstrates that dynamic RDS(ON) remains stable during aging.

To determine component switching lifetime, our SALT validation applies accelerated hard-switching stress as described in “A General Method for Determining GaN FET Switching Lifetime.” The TI model directly calculates the switching lifetime using the switching waveforms and shows that TI’s GaN FETs will not fail due to hard-switching stress over the entire product lifetime.

To verify the reliability of the power supply level, 64 TI GaN devices were DHTOL tested under strict power supply usage conditions . The devices showed stable efficiency, no hard failures, and demonstrated reliable operation for all power supply operation modes: hard and soft switching, third quadrant operation, hard commutation (reverse recovery), Miller breakdown at high slew rates, and reliable interaction with the driver and other system components. TI also verified surge robustness by applying surge strikes to the devices operating in the power supply under hard and soft switching operations and showed that TI's GaN FETs can effectively switch through bus voltage surges of up to 720V, providing significant margin. For more information on this test, see "A new method to verify the reliability of GaN FETs in power line surges under usage conditions."

Conclusion

The GaN industry has established a set of methods to ensure the reliability of GaN products, so the question is not "Is GaN reliable?" but "How to verify the reliability of GaN". TI GaN devices are reliable both at the component level and in actual applications, and GaN devices have passed the silicon qualification standards and GaN industry guidelines. In particular, TI's GaN products have passed JEP180, proving their reliability in power supply use.

Other References

• Browse TI's GaN product portfolio.

• Understand the advantages of GaN technology.