Impact of \hbox\hbox Passivation Thickness in Highly Scaled GaN HEMTs

• Published in: IEEE electron device letters 2012-07, Vol.33 (7), p.976-978
• Main Authors: Dong Seup Lee, Laboutin, O., Yu Cao, Johnson, W., Beam, E., Ketterson, A., Schuette, M., Saunier, P., Palacios, T.
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Capacitance; current collapse; current-gain cutoff frequency (f_{T}); fringing gate capacitance; Gallium nitride; GaN; hbox{Al}_{2}\hbox{O}_{3}; HEMTs; high-electron-mobility transistor (HEMT); Logic gates; MODFETs; Passivation
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2012.2194691

This letter studies the influence of the passivation thickness on the device characteristics of InAlGaN/GaN high-electron-mobility transistors with a gate length between sub-30 and 70 nm. As the Al 2 O 3 passivation thickness increases, the current collapse in 80-μs pulsed- I - V measurements decreases from 30% to 13%, while dc characteristics are almost unchanged with the exception of increasing drain-induced barrier lowering. The thicker passivation increases the fringing gate capacitance, which can be about 30% of the total gate capacitance in the devices with a gate length below 35 nm. This capacitance results in a significant drop of current-gain cutoff frequency ( f T ), and its effect is more important in the shorter gate length devices.