The Effects of Aging on the Intermodulation Distortion Levels of GaN HEMT Devices

Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) have been widely adopted into several wireless industries due to their advantages over competing RF amplifier technologies in output power, bandwidth, and efficiency. The reliability of GaN devices has been widely reported , but most published results focus on intrinsic degradation and aging effects of typical performance parameters. Legacy industry qualification guidelines, such as JEDEC JEP118, specify using a 1-dB drop in output power or a 20% drop in trans-conductance as examples of failure criteria for estimating product lifetimes. The typical Device-Under-Test (DUT) used in most test reporting is a relatively small, discrete Field Effect Transistor (FET). This is a valid approach for technology development, but GaN has now matured to the point where large multi-stage high-power RF devices are being utilized in emerging communications systems. With the focus shifting to system and network reliability, application-specific testing can be vital for characterizing the effects of GaN devices on system reliability. In a system, other parameters that are not tracked during a typical intrinsic reliability test can dramatically impact performance assurance with time.

An example of such a parameter is inter-modulation distortion (IMD), which is a critical figure-of-merit (FOM) in communication system designs such as software-defined radio (SDR) and 5G New Radio (NR) digital transmitters. If IMD characteristics of the power amplifier’s semiconductor device suffers any signal linearity degradation with age and environment effects, it would harm the overall performance of the communication system and network. Accel-RF Instruments Corporation has developed a novel test method for investigating aging effects on 3rd order inter-modulation distortion (IMD3) levels.