Gao F, Chen D, Lu B, et al. Impact of moisture and fluorocarbon passivation on the current collapse of AlGaN/GaN HEMTs[J]. IEEE electron device letters, 2012, 33(10): 1378-1380.

ABSTRACT

In  this  letter,  ambient  moisture  has  been  identi-fied  as  a  previously  unrecognized  cause  of  current  collapse  inAlGaN/GaN high-electron-mobility transistors. Unpassivated de-vices  exposed  to  dry  air  or  protected  with  a  hydrophobic  passi-vation,  such  as  vapor-deposited  fluorocarbon,  showed  negligiblecurrent collapse under 250-ns pulsed measurements. A mechanismbased on the ionization and deionization of the water molecules atthe device surface has been proposed to explain this behavior. Theuse of a hydrophobic passivation to prevent dc-to-RF dispersionworks even when it is not directly in contact with the semiconduc-tor surface, which allows the engineering of multistack passivationlayers  to  eliminate  current  collapse  while  minimizing  parasiticcapacitance.