Analysis of Trapping Effect on Large-Signal Characteristics of GaN HEMTs Using X-Parameters and UV Illumination

Kun Ming Chen*, Chuang Ju Lin, Chia Wei Chuang, Hsuan Cheng Pai, Edward Yi Chang, Guo Wei Huang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


GaN high-electron-mobility transistors (HEMTs) have attracted widespread attention for high-power microwave applications, owing to their superior properties. However, the charge trapping effect has limitations to its performance. To study the trapping effect on the device large-signal behavior, AlGaN/GaN HEMTs and metal-insulator-semiconductor HEMTs (MIS-HEMTs) were characterized through X-parameter measurements under ultraviolet (UV) illumination. For HEMTs without passivation, the magnitude of the large-signal output wave ((Formula presented.)) and small-signal forward gain ((Formula presented.)) at fundamental frequency increased, whereas the large-signal second harmonic output wave ((Formula presented.)) decreased when the device was exposed to UV light, resulting from the photoconductive effect and suppression of buffer-related trapping. For MIS-HEMTs with SiN passivation, much higher (Formula presented.) and (Formula presented.) have been obtained compared with HEMTs. It suggests that better RF power performance can be achieved by removing the surface state. Moreover, the X-parameters of the MIS-HEMT are less dependent on UV light, since the light-induced performance enhancement is offset by excess traps in the SiN layer excited by UV light. The radio frequency (RF) power parameters and signal waveforms were further obtained based on the X-parameter model. The variation of RF current gain and distortion with light was consistent with the measurement results of X-parameters. Therefore, the trap number in the AlGaN surface, GaN buffer, and SiN layer must be minimized for a good large-signal performance of AlGaN/GaN transistors.

Original languageEnglish
Article number1011
Issue number5
StatePublished - May 2023


  • GaN
  • HEMT
  • large-signal characterization
  • trapping effect
  • UV illumination
  • X-parameter


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