OHMIC CONTACTS AND SCHOTTKY BARRIERS TO N-GAN

Gallium nitride is a highly promising wide bandgap semiconductor with applications in high power electronic devices and optoelectronic devic es. For these devices to be realized, metallization, both ohmic and re ctifying must be available. In this manuscript, we discuss the propert ies of ohmic contacts and Schottky barriers on n-type GaN. The most re cent ohmic metallization scheme involves Ti/Al based composites, namel y Ti/Al/Ni/Au (150 Angstrom/2200 Angstrom/400 Angstrom/500 Angstrom.) preceded by a reactive ion etching (RIE) process which most likely ren ders the surface highly n-type. With annealing at 900 degrees C for 30 s, contacts with specific resistivity values less than rho(s) = 1 x 1 0(-7) Omega cm(2) for a doping level of 4 x 10(17) cm(-3) were obtaine d. Schottky barriers with Ti, Cr, Pd, Au, Ni, and Pt have been reporte d; however, we will concentrate here on Pt based structures as they yi eld a large barrier height of 1.1 eV. Both capacitance-voltage and cur rent-voltage analyses have been carried out as a function of temperatu re to gain insight into the current conduction processes involved. Att ention must now be turned to the modifications needed to render these contacts reliable.