Improving the ohmic properties of contacts to P–GaN by adding p–type dopants into the metallization layer

Abstract

The work investigates an increase of the density of free charge carriers in the sub-surface region of p-GaN by adding p-type dopants into the Ni-O layer of an Au/Ni-O metallization structure. We have examined electrical properties and concentration depth profiles of contact structures Au/Ni-Mg-O/p-GaN and Au/Ni-Zn-O/p-GaN, thus with magnesium and zinc as p-type dopants. The metallization layers were deposited on p-GaN by DC reactive magnetron sputtering in an atmosphere with a low concentration of oxygen (0.2 at%). The contacts were annealed in N2 . We have found that the structures containing magnesium or zinc exhibit lower values of contact resistivity in comparison with otherwise identical contacts without Mg or Zn dopants. In our opinion, the lower values of contact resistivity of the structures containing of Mg or Zn are caused by an increased density of holes in the sub-surface region of p-GaN due to diffusion of Mg or Zn from the deposited doped contact layers.

Improving the Ohmic Properties of Au/Ni–Mg/P–GaN Contacts by Adding Swcnt Metallization Interlayer Between Metal and P–GaN Layers

“…In [11] it was reported that by adding p-type dopants (Mg or Zn) into the Ni-O layer brought about an increase in the density of free charge carriers in the sub-surface region of p-GaN resulting in lower values of contact resistivity in comparison with otherwise identical contacts without dopants. In our opinion the further improvement of the ohmic properties of the Au/Ni-Mg-O/p-GaN contact by adding the SWCNT interlayer between the metal Au/NiMg(-O) and p-GaN layers is related to the existence of a contact scheme metal/p-SWCT/p-GaN.…”

“…Promising results were reached by incorporating group II dopants into the metallization layer intended to increase the charge carrier concentration in the surface region of p-GaN [9,10]. Contact structures Au/Ni-Mg-O/p-GaN and Au/Ni-Zn-O/pGaN exhibited lower values of specific contact resistance than the same structures without Mg and Zn dopants [11].…”

Ohmic Conacts to p-GaN on the Basis of Carbon Nanomaterials

“…The ohmic nature of these contacts is predetermined by formation of a thin oxide layer (NiO) at the metal/p-GaN interface. Incorporation group II dopants (Mg, Zn) into the Ni metallization layer intended to increase the charge carrier concentration in the surface region of p-GaN resulted in lower values of the specific contact resistance than in the same structures without Mg and Zn dopants [7][8][9].…”