Investigation of degradation for ohmic performance of oxidized Au/Ni/Mg-doped GaN

Abstract

The mechanism of ohmic contact degradation for the oxidized Au/Ni/Mg-doped GaN under various annealing times has been investigated. According to the results from x-ray photoelectron spectroscopy and the Cserveny’s concept, we found that an increase of hole concentration of NiOx would lead to the increasing barrier height and the increasing specific contact resistance (ρc) of oxidized Au/Ni/Mg-doped GaN. This suggests that the NiOx plays an important role in increasing (or reducing) the ρc of oxidized Au/Ni/Mg-doped GaN.

Nonalloyed ohmic contact formation in Ti/Al contacts to n-type AlGaN

“…The I -V curve obtained is linear for the samples from group C, while it has nonlinear curvature for the samples from group A or B. It indicates that ohmic performance can be obtained for the Al/Ti/n-AlGaN sample from group C. Then the specific contact resistance was measured using the TLM applied to a structure with the gap spacing between 5 and 60 µm [17,18]. The associated resistance as a function of the gap spacing for the Al/Ti/n-AlGaN sample from group C can be obtained.…”

“…On the other hand, the specific contact resistance was measured by the transmission line method (TLM) [16]. TLM patterns were performed using standard photolithography and lift-off techniques [16][17][18]. Ti/Al was used as the electrode, deposited on top of the n-AlGaN sample from group A, B or C. Ti(50 nm)/Al(150 nm) contacts were formed by a SC5750 sputter coater.…”