Impact of carbon impurities on the initial leakage current of AlGaN/GaN high electron mobility transistors

• Published in: Microelectronics and reliability Vol. 88-90; pp. 393 - 396
• Main Authors: Sasangka, W.A., Gao, Y., Gan, C.L., Thompson, C.V.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-09-2018
• Subjects: AlGaN/GaN HEMTs; Carbon impurities; EELS; Leakage current; Schottky barrier height; TEM; AlGaN/GaN HEMTs; Carbon impurities; Leakage current; Schottky barrier height; TEM; EELS
• ISSN: 0026-2714; 1872-941X
• DOI: 10.1016/j.microrel.2018.06.048

We have systematically studied the origin of high gate-leakage currents in AlGaN/GaN high electron mobility transistors (HEMTs). Devices that initially had a low gate-leakage current (good devices) are compared with ones that had a high gate-leakage current (bad devices). The apparent zero-bias Schottky barrier height of bad devices (0.4 < ϕB0 < 0.62 eV) was found to be lower than that of the good devices (ϕB0 = 0.79 eV). From transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) analysis, we found that this difference is due to the presence of carbon impurities in the nickel layer in the gate region.
•Presence of carbon impurities in the nickel layer causes a very high initial leakage current in AlGaN/GaN HEMTs devices.•Carbon reduces the zero-bias Schottky barrier height of nickel.•Possible source of carbon impurities is discussed.