Electrical properties of Pd-based ohmic contact to p-GaN

We have investigated the ohmic contact formation mechanism of Pd-based ohmic contacts to Mg-doped p-GaN grown by metalorganic chemical-vapor deposition. To examine room-temperature ohmic behavior, various metal contact systems were deposited and current–voltage measurements were carried out. In spite of the large theoretical Schottky barrier height between Pd and p-GaN, Pd-based contacts showed perfect ohmic characteristic even before annealing. According to the results of synchrotron x-ray radiation, the Pd (111) layer grew epitaxially on GaN (0001) surfaces with Pd[110]∥GaN[1120]. The closed-packed atomic planes of the Pd film were quite well ordered in surface normal direction, as well as in the in-plane direction. The effective Schottky barrier height of Au/Pd/Mg/Pd/p-GaN was 0.47 eV, which was estimated by the Norde method. This discrepancy between the theoretical barrier height and the measured one may be due to the epitaxial growth of Pd contact metal.

[1]  Volker Heine,et al.  Theory of Surface States , 1965 .

[2]  I. Lindau,et al.  New and unified model for Schottky barrier and III–V insulator interface states formation , 1979 .

[3]  H. Norde.  A modified forward I‐V plot for Schottky diodes with high series resistance , 1979 .

[4]  J. Tersoff.  Schottky Barrier Heights and the Continuum of Gap States , 1984 .

[5]  Hideki Hasegawa,et al.  Unified disorder induced gap state model for insulator–semiconductor and metal–semiconductor interfaces , 1986 .

[6]  Theodore D. Moustakas,et al.  Metal contacts to gallium nitride , 1993 .

[7]  H. Morkoç,et al.  Large‐band‐gap SiC, III‐V nitride, and II‐VI ZnSe‐based semiconductor device technologies , 1994 .

[8]  S. Nakamura.  InGaN/AlGaN blue-light-emitting diodes , 1995 .

[9]  Hadis Morkoç,et al.  Electrical conduction in platinum–gallium nitride Schottky diodes , 1996 .

[10]  H. Morkoç,et al.  Ohmic contacts and schottky barriers to n-GaN , 1996 .

[11]  J. Massies,et al.  Epitaxial relationships between GaN and Al2O3(0001) substrates , 1997 .

[12]  Ohmic contact to GaN grown by MOCVD , 1997 .

[13]  Thomas N. Jackson,et al.  Investigation of the mechanism for Ohmic contact formation in Al and Ti/Al contacts to n-type GaN , 1997 .

[14]  R. F. Karlicek,et al.  Study of contact resistivity, mechanical integrity, and thermal stability of Ti/Al and Ta/Al ohmic contacts to n-type GaN , 1998 .

[15]  Jinn-Kong Sheu,et al.  Effects of thermal annealing on the indium tin oxide Schottky contacts of n-GaN , 1998 .

[16]  Jinn-Kong Sheu,et al.  The effect of thermal annealing on the Ni/Au contact of p-type GaN , 1998 .

[17]  Seong Jun Park,et al.  Formation of low resistance Pt ohmic contacts to p-type GaN using two-step surface treatment , 1999 .

[18]  Seong Jun Park,et al.  Low-resistance Pt/Ni/Au ohmic contacts to p-type GaN , 1999 .

[19]  L. J. Chen,et al.  Low-resistance ohmic contacts to p-type GaN achieved by the oxidation of Ni/Au films , 1999 .

[20]  Kelvin G. Lynn,et al.  Ohmic contact formation mechanism of nonalloyed Pd contacts to p-type GaN observed by positron annihilation spectroscopy , 1999 .

[21]  Current conduction mechanism of Si/Ti-based Ohmic contacts to n-GaN , 2000 .