Defect characterization in high-electron-mobility transistors with regrown p-GaN gate by low-frequency noise and deep-level transient spectroscopy

To investigate the defects from the gate regrowth process, samples with and without regrowth p-GaN process are fabricated by metalorganic chemical vapor deposition (MOCVD). The DC characteristics indicate larger gate leakage (I${}_{gs}$) between the GaN channel and the p-GaN gate in the regrowth sample than in the nonregrowth counterpart. In addition, significant Si/O impurities are introduced by the regrowth process at the interface between channel and regrown AlGaN barrier. The low-frequency noise (LFN) measurement and deep-level transient spectroscopy (DLTS) are further carried out to investigate the defectivity at the AlGaN barrier and channel interface, giving a 2-3 times higher border trap density in the AlGaN barrier (depth $\approx$5 nm from the channel interface) and a 10 times increase in interface trap density at the channel interface, corresponding with a band of shallow levels E3 = E${}_c$-0.02-0.15 eV. Three additional bulk traps E2/E5 (E${}_c$-0.8 eV, ${\sigma }_n$ = 5 $\times$ 10${}^{-15}$ cm${}^2$ / E${}_c$-0.17 eV, ${\sigma }_n$ = 5 $\times$ 10${}^{-22}$ cm${}^2)$ and E4 (E${}_c$-0.23 eV, ${\sigma }_n$ = 5 $\times$ 10${}^{-19}$ cm${}^2)$ are also found in the regrowth and nonregrowth samples, respectively. Their possible spatial locations and origins are discussed. (© 2021 Wiley‐VCH GmbH)