THERMAL-STABILITY OF W AND WSIX CONTACTS ON P-GAN

The annealing temperature (400-1100 degrees C) and measurement tempera ture (25-300 degrees C) dependencies of current-voltage characteristic s of W and WSi0.45 contacts on p-GaN have been compared to the more co mmon Ni/Au metallization. At 25 degrees C, slightly rectifying charact eristics were obtained for all three types of contact, but at 300 degr ees C specific contact resistances in the 10(-2) Omega cm(2) range wer e obtained for WSi0.45 and Ni/Au. This is due to an increase in Mg acc eptor ionization efficiency (from 10% at 25 degrees C to 57% at 300 de grees C) and more efficient thermionic hole emission across the metal- GaN interface. Both WSi0.45 and W contacts retained featureless surfac e morphology for annealing at >900 degrees C, whereas Ni/Au showed sub stantial islanding at less than or equal to 700 degrees C. (C) 1998 Am erican Institute of Physics.