Low-resistance Ni/Al Ohmic contacts applied to a nonpolar a-plane n-type GaN

Abstract

The authors report upon a low-resistance Ni/Al Ohmic contact to a nonpolar n-type a-plane GaN with respect to the annealing temperature. The Schottky behavior of the Ni/Al contact changes to a linear Ohmic behavior at a 700 °C annealing, at which the specific contact resistivity of the Ni/Al contact became as low as 5.8×10−5 whereas that of a typical Ti/Al contact was 1.6×10−3 Ω cm2. This improvement is attributed to a lowering of the Schottky barrier height via a Ni–Al interdiffused layer, formed at the interface between the metal and the nonpolar a-plane n-type GaN during the annealing process.

Self-supported hierarchical hollow-branch cobalt oxide nanorod arrays as binder-free electrodes for high-performance lithium ion batteries

“…Additionally, our results are higher than template-free synthesized SnO 2 and Fe 2 O 3 hollow spheres and particles [16]. Our samples also show good 6 cyclability with specific capacity of 695.5 mAh g -1 at 0.5 A g -1 and 635.8 mAh g -1 at 1 A g -1 after 150 cycles, respectively (Fig. 2d).…”

“…To date, transitional metal oxides have been widely studied as promising candidates because of their high specific capacity, typically 2-3 times higher than that of the carbon based materials [3][4][5]. Among them, CoO has attracted increasing attention due to its high theoretical capacity (718 mAh g -1 ) [6], arising from the reversible electrochemical reaction with Li ion (CoO + 2Li + + 2e  Co + Li 2 O). However, similar to other metal oxides, the practical application of CoO as anode for LIBs is still hampered by two main issues: pulverization problem and fast capacity fading [7,8].…”

Improved device performance in nonpolar a ‐plane GaN LEDs using a Ni/Al/Ni/Au n‐type ohmic contact

“…The ρ c of the Ni/Al/Ni/Au sample was 5.6 × 10 –5 Ω cm 2 , about 10 times smaller than the 6.8 × 10 –4 Ω cm 2 of the typical Ti/Al/Ni/Au sample, at 700 °C annealing temperature. The reason that ρ c of the Ni/Al/Ni/Au contact to a ‐plane n‐type GaN decreases with increasing annealing temperature can be attributed to the reduction of the effective SBH via the interdiffused metallic compounds formed at the interface between the Ni interlayer and the a ‐plane n‐type GaN during the annealing process, as reported in 8.…”

“…At present, a Ti/Al metal scheme is typically used for n‐type ohmic contacts to a ‐plane GaN 7, but it has problems involving the increase of the specific contact resistivity ( ρ c ) with annealing temperatures, via the increase of the Schottky barrier height (SBH) between the metal and the a ‐plane n‐type GaN. In our previous work, we proposed a unique Ni/Al metal scheme as an alternative, and successfully demonstrated low‐resistance n‐type ohmic properties on a ‐plane GaN 8.…”

Schottky characteristics of Pt contacts on (11–22) semipolar n-type GaN grown on m-plane sapphire substrates

“…[9] The Ohmic and Schottky characteristics of nonpolar n-GaN grown on r-plane sapphire substrates have also been investigated by several groups. [10][11][12] However, studies on the electrical characteristics and carrier transport mechanism of the Ohmic or Schottky contacts on semipolar n-GaN grown on m-plane sapphire substrates remain very rare. Due to this gap in the literature, this study investigates the electrical characteristics of Pt Schottky diodes fabricated on semipolar n-GaN, in which a Ti/Al layer was used as the Ohmic contact.…”