Structural and electrical characterization of AuPdAlTi ohmic contacts to AlGaN∕GaN with varying Ti content

AuPdAlTi∕AlGaN∕GaN ohmic contact structures with varying Ti:Al ratios have been investigated. The relationship between Ti:Al ratio, interfacial microstructure, and contact resistance is examined. Rapid thermal annealing temperatures of 850°C or higher are required to produce an ohmic contact with annealing at 950°C producing the lowest contact resistance in the majority of samples. Samples annealed at 950°C have been analyzed using complementary transmission electron microscopy and electrical characterization techniques. A thin Ti-nitride region is found to form at the contact/semiconductor interface in all samples. Ti-nitride inclusions through the AlGaN∕GaN layer are also observed, surrounded by an Al∕Au rich metallurgical barrier layer, with the size of the inclusions increasing with Ti content. The size of these inclusions does not have any clear effect on the electrical characteristics of the contacts at room temperature, but samples with fewer inclusions show superior electrical characteristics at h...

[1]  H. Gong,et al.  Electrical characterization and metallurgical analysis of Pd-containing multilayer contacts on GaN , 2001 .

[2]  J. Kwak,et al.  Low resistance Al/Ti/n-GaN ohmic contacts with improved surface morphology and thermal stability , 2000 .

[3]  H. Morkoç,et al.  Very low resistance multilayer Ohmic contact to n‐GaN , 1996 .

[4]  Y. Lin,et al.  Schottky barrier height and nitrogen–vacancy-related defects in Ti alloyed Ohmic contacts to n-GaN , 2004 .

[5]  Ho Won Jang,et al.  Mechanism for Ohmic contact formation of Ti on n-type GaN investigated using synchrotron radiation photoemission spectroscopy , 2002 .

[6]  A. Davydov,et al.  Interfacial reactions of Ti/n-GaN contacts at elevated temperature , 2003 .

[7]  H. Morkoç,et al.  Photoluminescence characterization of the quantum well structure and influence of optical illumination on the electrical performance of AlGaN/GaN modulation‐doped field‐effect transistors , 1996 .

[8]  H. Morkoç,et al.  Microstructure of Ti/Al and Ti/Al/Ni/Au Ohmic contacts for n-GaN , 1996 .

[9]  H. Morkoç,et al.  Low resistance ohmic contacts on wide band‐gap GaN , 1994 .

[10]  Ching-Ting Lee,et al.  Long-term thermal stability of Ti/Al/Pt/Au Ohmic contacts to n-type GaN , 2000 .

[11]  Y. L. Chen,et al.  High performance AlGaN/GaN HEMT with improved ohmic contacts , 1998 .

[12]  R. A. Davies,et al.  Correlation of contact resistance with microstructure for Au/Ni/Al/Ti/AlGaN/GaN ohmic contacts using transmission electron microscopy , 2001 .

[13]  Michael J. Uren,et al.  Structural and electrical characterization of AuTiAlTi/AlGaN/GaN ohmic contacts , 2002 .