Nonalloyed Cr∕Au-based Ohmic contacts to n-GaN

Abstract

Nonalloyed Cr/ Au-based metal contacts to n-GaN have been demonstrated. The deposited Au/ Cr/ n-GaN contacts exhibited a specific contact resistance ͑ c ͒ of approximately 5.6 ϫ 10 −5 ⍀ cm 2. Although the nonalloyed Ti/ Al-based contacts to n-GaN can also exhibit a comparable c value, their thermal stability is inferior to the Cr/ Au-based contacts. This could be attributed to the fact that Al tends to ball up during thermal annealing. Thus, the surface morphology of most of the annealed Ti/ Al-based contacts was quite rough, and the contacts became rectified when they were annealed at a temperature below 700°C. However, the annealed Cr/ Au-based contacts exhibited an Ohmic characteristic and had a smooth surface when annealing temperatures did not exceed 700°C. In addition, the thermal stability could be further improved by inserting a Pt layer between the Cr and Au layers. This scheme could prevent the diffusion of Au into the Cr layer, thus preventing Au from reaching the Cr/ GaN interface where it could form a possible Ga-Au phase, which would degrade the Ohmic contacts.

Термическая стабильность несплавных омических контактов к гетероструктурам AlGaN/GaN

“…• C появля-ется неомичность контакта металл−полупроводник, характеризующая-ся нелинейной вольт-амперной характеристикой [4,5]. Поскольку СВЧ МИС в процессе изготовления проходят технологические операции с температурой процесса 300−350…”

Non-alloyed Cr/Au Ohmic contacts to N-face and Ga-face n-GaN

“…The Ti/Al-based contacts are the most popular metal schemes for n-GaN due to their low work function. However, they do not alleviate the need for high annealing temperatures to form intermetallic alloys further with low work function at the metal/semiconductor interface [5]. The effect of thermal annealing on the electrical property of metal contacts was different between the Ti/Al-and Cr/Au-based contacts on the Ga-face n-GaN surface [5].…”

“…However, they do not alleviate the need for high annealing temperatures to form intermetallic alloys further with low work function at the metal/semiconductor interface [5]. The effect of thermal annealing on the electrical property of metal contacts was different between the Ti/Al-and Cr/Au-based contacts on the Ga-face n-GaN surface [5]. Several reports have recently revealed that Al-based metal contacts could form low-resistivity Ohmic contacts on the N-face n-GaN surface [6,7].…”

“…Metal contacts on Ga-face n-GaN surface have been widely studied in the past decade. Different metals, such as Ti/Al-and Cr/Au-based metals, have been proven to exhibit good Ohmic contact property and stability when deposited on the Ga-face n-GaN surface [5]. The Ti/Al-based contacts are the most popular metal schemes for n-GaN due to their low work function.…”

Ultra-thin films for plasmonics: a technology overview

“…Two of the most used adhesion layers are chromium [44,45] and titanium. Although they allow for a smoother and thinner waveguide, neither of these metals has the optical characteristics superior to gold; thus, the plasmon behavior can worsen significantly.…”