“The adoption of gallium nitride (GaN) field-effect transistors (FETs) is rapidly increasing due to their ability to increase efficiency and reduce power supply size. But before investing in the technology, you might still be wondering if GaN is reliable. I’m surprised no one has asked if silicon is reliable. After all, there are still new silicon products coming out, and power supply designers are also very concerned about the reliability of silicon power devices.
The adoption of gallium nitride (GaN) field-effect transistors (FETs) is rapidly increasing due to their ability to increase efficiency and reduce power supply size. But before investing in the technology, you might still be wondering if GaN is reliable. I’m surprised no one has asked if silicon is reliable. After all, there are still new silicon products coming out, and power supply designers are also very concerned about the reliability of silicon power devices.
In fact, the GaN industry has put a lot of effort and time into reliability.
Questions about silicon reliability are worded differently, such as “Is this qualified?” Although GaN devices are also silicon qualified, power supply manufacturers are still not convinced that a silicon approach can ensure the reliability of GaN FETs. This is a reasonable point since not all silicon device testing is applicable to GaN, and traditional silicon qualification itself does not include stress testing for the actual switching conditions of power supply usage. The JEDEC JC-70 Wide Bandgap Power Electronics Conversion semiconductor Committee has issued several GaN-specific guidelines to address such deficiencies.
Understanding the reliability of GaN products
Read the technical white paper “Achieving Lifetime Reliability for 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 increased dynamic drain-source on-resistance (RDS(ON)). Figure 1 outlines 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 testing according to traditional silicon standards, using GaN-specific test methods, and determining lifetime by applying accelerated stress until the device fails. At the power level, the device is operated under the stringent operating conditions of the relevant application. TI has also verified the robustness of the device under extreme operating conditions in the event of an event.
Reliability of GaN FETs in Applications
JEDEC JEP180 guidelines provide a general approach to ensuring 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 the relevant stresses and operate reliably under the stringent operating conditions of the power supply. The former demo uses Switch Accelerated Life Testing (SALT) to stress test the device, while the latter uses Dynamic High Temperature Operating Life (DHTOL) testing.
Devices are also subject to extreme operating conditions in practice, 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 its overvoltage capability, GaN FETs do not go into avalanche breakdown, but instead switch through surge shocks. Having overvoltage capability also improves system reliability because the avalanche FET cannot absorb much of the avalanche energy, so the protection circuit must absorb most of the surge. As they age, surge absorbing components degrade, subjecting 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 qualified its GaN products according to the method shown in Figure 1. Figure 2 summarizes the results, showing results from the component-level and power-level modules.
Figure 2: Using the method shown in Figure 1, the reliability of GaN FETs was verified through GaN-specific guidelines.
At the component level, TI GaN passes traditional silicon qualification with high reliability for GaN-specific failure mechanisms. TI designed and validated its GaN products for high reliability against time-dependent breakdown (TDB), charge trapping, and hot electron depletion failure mechanisms, and demonstrated that dynamic RDS(ON) remains stable during aging.
To determine component switching lifetime, our SALT verification applies accelerated hard switching stress, as described in “General Approach to Determining GaN FET Switching Lifetime” TI models use switching waveforms to directly calculate switching lifetime and show that TI’s GaN FETs are No failure during life due to hard switching stress.
To verify power level reliability, we performed DHTOL testing on 64 TI GaN devices under stringent power usage conditions. Such devices show stable efficiency with no hard faults, showing reliable operation for all modes of power operation: hard and soft switching, third quadrant operation, hard commutation (reverse recovery), high slew rate Miller breakdown, and reliable interaction with drivers and other system components. TI has also verified surge robustness by applying surge shocks to devices operating in the power supply under both hard-switching and soft-switching operations, and has shown that TI’s GaN FETs can efficiently switch through bus voltage surges up to 720V, providing significant margin. To learn more about this test, see “A New Approach to Verify GaN FET Reliability in Power Line Surge Under Service Conditions”.
The GaN industry has established a methodology 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 at the component level and in real-world applications, and GaN devices have passed silicon qualification standards and GaN industry guidelines. In particular, TI’s GaN products have passed JEP180, proving their reliability in power usage.