Transcript 下載/瀏覽Download

Indium as an efficient ohmic contact
to N-face n-GaN of GaN-based vertical
light-emitting diodes
Seon Young Moon, Jun Ho Son, Kyung Jin
Choi, Jong-Lam Lee, and Ho Won Jang
APPLIED PHYSICS LETTERS 99, 202106
(2011)
報告者: C.C.Shan
Outline
 Introduction
 Band-diagram
 Experiment
 Conclusion
Introduction
We propose indium (In), a low work function and nitrideforming element, as an efficient ohmic contact layer to Nface n-GaN.
While conventional Al-based ohmic contacts
show severe degradation after annealing at 300 C, Inbased ohmic contacts display considerable improvement
in contact resistivity.
The annealing-induced enhancement of ohmic behavior in
In-based contacts is attributed to the formation of an InN
interfacial layer, which is supported by x-ray photoemission
spectroscopy measurements.
These results suggest that In is of particular importance for
application as reliable ohmic contacts to n-GaN of GaNbased vertical light-emitting diodes.
Band-diagram
 簡易結構及能帶圖
Schematic band diagrams for (a) Al/AlN/N-face n-GaN and (b)
In/InN/N-face n-GaN structures. PS and PP denote spontaneous
polarization and piezoelectric polarization, respectively. For an InN
epilayer on N-face n-GaN, PS is calculated to be 0.032 C/m2 and PP is
0.241 C/m2.
Experiment
 I-V curve結果
(a) and (b) Typical IV curves of Al (200 nm) and In
(200 nm) contacts to N-face n-GaN before and after annealing.
Experiment
 接觸電阻實驗結果
Contact resistivities of the Al and In contacts as a function of annealing temperature.
Experiment
 XPS量測結果
XPS spectra of
(a) Ga2p3/2
(b) In 3d5/2 core levels
for as-deposited and
300 C-annealed In
(10A ° ) contacts on
N-face n-GaN. All
In3d5/2 peaks were
fitted using a Shirley
background and mixed
Lorentzian–-Gaussian
line shapes.
Experiment
 I-V curve 量測結果
Typical IV curves of Ti/Al (50/200 nm) and In/Ti/Al (200/50/200 nm) contacts
to N-face n-GaN before and after annealing at 300 C and 450 C.
Conclusion
We have demonstrated that low resistance ohmic contacts
to N-face n-GaN are achieved using In. While conventional
Al-based contacts showed severe degradation after
annealing at 300 C, In-based contacts displayed
considerably improved ohmic behaviors after annealing.
The origin of the ohmic contact formation and the annealing
induced improvement was discussed with the formation of
an interfacial InN layer. Our results prove that In-based
ohmic contacts can be utilized as reliable electrodes to Nface n-GaN of GaN-based vertical LEDs for solid-state
lighting.
Thanks for your attention