Effects of reactive ion etching on the electrical characteristics of GaN

We present an investigation of the electrical characteristics of plasma exp osed GaN. The specific contact resistance of ohmic contacts fabricated on G aN after argon plasma bombardment for 2.5 min at. 0.03 W/cm(2) are measured to decrease by a factor of 4 compared to the unetched surface. Gold has be en found to be the best material for GaN Schottky diode. A study of the ele ctrical performance of diodes fabricated on plasma exposed GaN has been und ertaken. To compare the effect of the chemical versus physical factors, as well as the role played by the ion mass of the etchant species during the e tching process on diode behavior, GaN surfaces have been exposed to Ar, N-2 , as well as SF6+N-2 plasmas before diode fabrication. Our data indicate th at a plasma with low ion mass etchant species or a dominant chemical mechan ism of etching with a high etch rate creates less surface damage. The use o f a SF6+N-2 plasma should be possible for GaN transistor gate recessing. (C ) 2000 American Vacuum Society. [S0734-211X(00)07306-6].