Y. Kribes et al., INVESTIGATION OF ALUMINUM OHMIC CONTACTS TO N-TYPE GAN GROWN BY MOLECULAR-BEAM EPITAXY, Semiconductor science and technology, 12(11), 1997, pp. 1500-1505
Using epi-layers of different doping concentrations, we have investiga
ted aluminium contacts on n-type gallium nitride grown by plasma sourc
e molecular beam epitaxy. To achieve repeatable and reliable results i
t was found that the semiconductor needed to be etched in aqua-regia b
efore the deposition of the contact metallization. Scanning electron m
icrographs of the semiconductor surface show a deterioration of the se
miconductor surface on etching. The specific contact resistivity of th
e etched samples were, however, superior. Annealing the contacts at 60
0 degrees C produced contacts with the lowest specific contact resista
nce of 2.0 x 10(-4) Ohm cm(2). The long-term aging of these contacts w
as also investigated. The contacts and the sheet resistance were both
found to deteriorate over a three-month period.