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Title: Interfacial reaction and surface morphology of Pd/Re contact schemes to p-type GaN
Authors: Reddy, V Rajagopal
Ramesh, C K
Reddy, P Narasimha
Keywords: interfacial reaction
Pd/Re contacts
surface morphology
glancing angle XRD
Auger depth profiling
Issue Date: May-2004
Publisher: CSIR
IPC CodeH 01 C 10/00
Abstract: The interfacial reactions between the Pd (20 nm) / Re (25 nm) contacts and p-GaN(1.13×1017cm-3) have been investigated using glancing angle XRD and Auger depth profiling. The samples are annealed at temperatures of 550 ºC and 650 ºC for 1 min in a nitrogen ambient. The I-V measurements show that the as-deposited sample is ohmic with a contact resistance of 1.4×10-3 Ω cm2. However, the annealing of the sample at 550 ºC results in much better ohmic behaviour with a specific contact resistance of 8.7×10-4 Ω cm2. Further, increase in annealing temperature (650 ºC) causes the degradation of the ohmic property. Based on AES and XRD results, the formation of Ga-Pd reaction phases results in the generation of Ga vacancies at the GaN surface region, which plays a role in reducing contact resistivity. The AFM results show that the surface morphology of the as-deposited contact is fairly smooth (with a rms roughness of 1.7 nm) and when annealed at 550 °C, contact has become somewhat degraded with a root-mean-square roughness of 6.5 nm.
Page(s): 361-365
ISSN: 0975-1041 (Online); 0019-5596 (Print)
Source:IJPAP Vol.42(05) [May 2004]

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