Impact of Charge-Trapping Effects on Reliability Instability in Al(x)Ga(1−x)N/GaN High-Electron-Mobility Transistors with Various Al Compositions

In this study, we present a detailed analysis of trapping characteristics at the Al(x)Ga(1−x)N/GaN interface of Al(x)Ga(1−x)N/GaN high-electron-mobility transistors (HEMTs) with reliability assessments, demonstrating how the composition of the Al in the Al(x)Ga(1−x)N barrier impacts the performance of the device. Reliability instability assessment in two different Al(x)Ga(1−x)N/GaN HEMTs [x = 0.25, 0.45] using a single-pulse I(D)–V(D) characterization technique revealed higher drain-current degradation (∆I(D)) with pulse time for Al(0.45)Ga(0.55)N/GaN devices which correlates to the fast-transient charge-trapping in the defect sites near the interface of Al(x)Ga(1−x)N/GaN. Constant voltage stress (CVS) measurement was used to analyze the charge-trapping phenomena of the channel carriers for long-term reliability testing. Al(0.45)Ga(0.55)N/GaN devices exhibited higher-threshold voltage shifting (∆V(T)) caused by stress electric fields, verifying the interfacial deterioration phenomenon. Defect sites near the interface of the AlGaN barrier responded to the stress electric fields and captured channel electrons—resulting in these charging effects that could be partially reversed using recovery voltages. The quantitative extraction of volume trap density (N(t)) using 1/f low-frequency noise characterizations unveiled a 40% reduced N(t) for the Al(0.25)Ga(0.75)N/GaN device, further verifying the higher trapping phenomena in the Al(0.45)Ga(0.55)N barrier caused by the rougher Al(0.45)Ga(0.55)N/GaN interface.