Influence of the Pt barrier on Ti/Al/Pt/Au ohmic contacts to n-GaN studied by Rutherford backscattering spectrometry and x-ray diffraction

Abstract

The diffusion barrier effect of Pt has been investigated in Ti/Al/Pt/Au ohmic contacts to n-GaN. Severe indiffusion, outdiffusion of Pt and outdiffusion of Ga have been found in 450 • C annealed samples according to the Rutherford backscattering spectrometry (RBS) results. At the same time, the reaction between Ga and Pt has also been identified by glancing angle synchrotron irradiation x-ray diffraction (GASIXRD) in the samples annealed at 450 • C. A higher annealing temperature causes Pt to indiffuse into GaN and react with GaN further. As a result, electrical degradation of the Ti/Al/Pt/Au metallization system was found for samples aged at 600 • C. In contrast, no obvious degradation was found for the aged Ti/Al/Ni/Au samples. According to the RBS and GASIXRD results, it is suggested that the formation of Ga 3 Pt 5 may cause degradation in the electrical properties of the Ti/Al/Pt/Au metallization system.

Low resistivity ohmic contact to n-type poly-GaN using a Ti/Au/Ni/Au multilayer metal system

“…This is considered to be due to that most of the Ni atoms in the Au-Ni solid solution began to be driven out when the sample was annealed at higher temperatures. On the other hand, Hu et al [10] reported that the peak of Au(1 1 1) shifted all the way to an angle higher than 0.25°as the annealing temperature was increased above 450°C, which finding had been explained elsewhere by the formation of Au-Ga solution [13]. However, in this experiment, the peak of Au(1 1 1) did not shift further as the annealing temperature was increased above 500°C.…”

“…Accordingly, Au and Ni metals were deposited along the <1 1 1> direction, the preferred growth orientation on a (0 0 0 1) plane of GaN polycrystal. These results show that the epitaxial microstructures of Au and Ni were formed on the poly-GaN film [10,19]. Hence, the orientation relationships for Au/poly-GaN and Ni/poly-GaN are Au(1 1 1)//polyGaN(0 0 0 2) and Ni(1 1 1)//poly-GaN(0 0 0 2), respectively.…”

“…Numerous works of the ohmic contact of single crystalline GaN have been published. For n-type single crystalline GaN, low specific contact resistivities in the range 10 À6 -10 À8 X cm 2 were presented [3][4][5][6][7], while for ptype one, a range of 10 À3 -10 À6 X cm 2 has been claimed by using different multilayer metal systems [8][9][10][11][12][13][14]. However, the lattice mismatch and the misfit in the thermal expansion coefficients between GaN and the widely used sapphire or Si substrate are large.…”

GaN-cored heteronanowires sheathed with Pt shells: Preparation and annealing studies

“…On the other hand, platinum (Pt) is one of the most important transition metal, being used extensively in semiconductor devices including an electrode material for the capacitor structures in memory devices [5]. Additionally, Pt-based metallization schemes have been employed to obtain reliable ohmic contacts to p-GaN [6] and n-GaN [7]. Furthermore, since hydrogen atoms can diffuse very quickly towards Pt-GaN interface, the combination of GaN with catalytic Pt has been used to realize sensors for hydrogen and hydrocarbon gases [8].…”