Title :
Impact of Moisture and Fluorocarbon Passivation on the Current Collapse of AlGaN/GaN HEMTs
Author :
Gao, Feng ; Chen, Di ; Lu, Bin ; Tuller, Harry L. ; Thompson, Carl V. ; Keller, Stacia ; Mishra, Umesh K. ; Palacios, Tomás
Author_Institution :
Dept. of Electr. Eng. & Comput. Sci., Massachusetts Inst. of Technol., Cambridge, MA, USA
Abstract :
In this letter, ambient moisture has been identified as a previously unrecognized cause of current collapse in AlGaN/GaN high-electron-mobility transistors. Unpassivated devices exposed to dry air or protected with a hydrophobic passivation, such as vapor-deposited fluorocarbon, showed negligible current collapse under 250-ns pulsed measurements. A mechanism based on the ionization and deionization of the water molecules at the device surface has been proposed to explain this behavior. The use of a hydrophobic passivation to prevent dc-to-RF dispersion works even when it is not directly in contact with the semiconductor surface, which allows the engineering of multistack passivation layers to eliminate current collapse while minimizing parasitic capacitance.
Keywords :
III-V semiconductors; aluminium compounds; gallium compounds; high electron mobility transistors; ionisation; moisture; passivation; wide band gap semiconductors; AlGaN-GaN; HEMT; ambient moisture impact; current collapse; dc-to-RF dispersion; device surface; fluorocarbon passivation; high-electron-mobility transistors; hydrophobic passivation; multistack passivation layers; parasitic capacitance; pulsed measurements; semiconductor surface; time 250 ns; unpassivated devices; vapor-deposited fluorocarbon; water molecule deionization; water molecule ionization; Aluminum gallium nitride; Current measurement; Gallium nitride; HEMTs; MODFETs; Moisture; Passivation; AlGaN/GaN high-electron-mobility transistors (HEMTs); current collapse; moisture; passivation;
Journal_Title :
Electron Device Letters, IEEE
DOI :
10.1109/LED.2012.2206556