Experimental investigation on the performance degradations of the GaN class-F power amplifier under humidity conditions

Significance 

Rapid advancement in wireless communication technology has significantly increased the demand for phased array radars and mobile and communication systems. In particular, GaN-based radio-frequency (RF) power amplifiers have drawn significant research attention owing to their remarkable reliability in high-temperature conditions, high voltage breakdown and high power capability properties. They form critical components of WCS comprising receiving and transmitting antennas. However, WCSs and antennas operating in outdoor environments are highly susceptible to environmental conditions, including temperature, humidity and pressure. Specifically, some reports show that about 10% of failures associated with electronic equipment at the United States coastline lines are due to moisture content. And the failures are more common in WCSs comprising power amplifiers. Therefore, evaluating the performance of power amplifiers under different humidity conditions is highly desirable.

The performance of different types of electronic equipment like capacitors and photodiodes have been experimentally evaluated under varying environmental conditions. However, these studies concentrate on the effects of temperature and humidity on the lifetime of the devices. Very few studies have focused on the effects of degradation due to environmental conditions on the device performance. Most power amplifiers used in outdoor application systems get degraded even before reaching the end of their lifetime. Generally, the performance degradation of power amplifiers can be directly attributed to system failures. Therefore, it is important to pay attention to the duration of the power amplifier to achieve the acceptable performance limits instead of the time it should work throughout its life.

Generally, the lifetime of key specifications of power amplifiers is significantly affected by humidity. A thorough understating humidity dependency of power amplifier specifications is critical in determining its performance and lifetime. To this note, Dr. Shaohua Zhou from Tianjin University investigated the performance degradation of the GaN class-F power amplifier under varying humidity conditions. The humidity experiments Vötsch Industrietechnik SC3 1000 MHG environmental test chamber. Specifically, the author investigated the effects of humidity on the key power amplifier specifications such as drain current, power-added efficiency (PAE), large-signal gain and power output. The experimental results were measured to aid discussion and analysis of the possible reasons for the performance deterioration. The work is currently published in the journal, Semiconductor Science and Technology.

Results show that an increase in humidity degrades the key specifications of power amplifiers, including large-signal gain, power output and PAE characteristics of the GaN class F- power amplifiers. The performance degradation could be attributed to the decrease in the 2DEG mobility density caused by the degradation of the surface at AlGaN recess regions due to the diffusion mechanism of the Al and Ga. Moreover, the 2DEG mobility alongside threshold voltage also contributed to the degradation of the drain current. Furthermore, a theoretical analysis demonstrated that a positive drift of GaN HEMT’s threshold voltage and a decrease of the 2DEG mobility of the GaN HEMT with an increase in the humidity would result in a reduction of the drain current.

In a nutshell, the author experimentally investigated the humidity dependency of key specifications of GaN class-F power amplifiers. The focus was on the effects of humidity on the degradation performance of the key specifications of the GaN class-F power amplifiers, which is quite different from determining the life of power amplifiers due to humidity. The study insights provide opportunities for testing the feasibility of the theoretical theory besides contributing to the understating of the effects of humidity on the key specifications of GaN class-F power amplifiers. In this paper, an exploratory study is conducted around the key specification degradation of electronic devices using PA as an example. Not strictly speaking, the study of specification degradation of electronic devices can also be said to be the version 2.0 of reliability research. This is a new and highly significant research area. In a statement to Advances in Engineering, Dr. Shaohua Zhou said that the research performed in the study provides another angle to handle the practical working environments rather than the extreme cases as the reliability study.

Reference

Zhou, S. (2021). Experimental investigation on the performance degradations of the GaN class-F power amplifier under humidity conditionsSemiconductor Science and Technology, 36(3), 035025.

Go To Semiconductor Science and Technology

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