Premium
The Significant Effect of Carbon and Oxygen Contaminants at Pd/p‐GaN Interface on Its Ohmic Contact Characteristics
Author(s) -
Li Zhengcheng,
Huang Rong,
Chen Xiao,
Wang Hu,
Feng Boyuan,
He Gaohang,
Huang Zengli,
Li Fangsen,
Liu Jianping,
Zhang Liqun,
Liu Tong,
Ding Sunan
Publication year - 2021
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.202000603
Subject(s) - ohmic contact , metalorganic vapour phase epitaxy , contact resistance , materials science , chemical vapor deposition , schottky barrier , annealing (glass) , oxide , analytical chemistry (journal) , metal , layer (electronics) , optoelectronics , nanotechnology , metallurgy , chemistry , epitaxy , diode , chromatography
A low‐resistance Ohmic contact of Pd/Pt/Au metallization scheme is formed on a p‐type GaN film grown by metal‐organic chemical vapor deposition (MOCVD). Two samples are prepared to explore the effect of contaminations at the metal and GaN interface on the properties of the Ohmic contact. One directly transfers the fresh GaN film from MOCVD to the metal deposition chamber through an ultrahigh vacuum (UHV) tube, without exposing the GaN surface to air; the other transfers the GaN film from MOCVD to metal deposition through the atmosphere. The results show a lower specific contact resistance (6.2 ± 0.9) × 10 −5 Ω cm 2 for the directly UHV‐transferred sample than the air‐transferred sample (2.1 ± 0.9) × 10 −4 Ω cm 2 . Once exposed to air, carbonaceous particles and an amorphous oxide layer easily adhere to the p‐type GaN surface, which not only increase the Schottky barrier height but also generate more grain boundaries in the Pd/Pt/Au stacks. The grain boundaries, acting as diffusion channels, make Au atoms diffuse easily into the Pd layer and propagate to the p‐GaN surface layer after annealing. Therefore, the Ohmic contact fabricated in UHV ambience with lower oxygen and carbon contaminations at the interface shows superior characteristics than the samples prepared by the traditional method.