Transparent Ohmic contacts of oxidized Ru and Ir on <i>p</i>-type GaN

Jang, Ho Won; Lee, Jong‐Lam

doi:10.1063/1.1565494

Cited by 32 publications

(9 citation statements)

References 18 publications

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“…It is known that RuO 2 is highly transparent with good electrical conductivity and high work function (45.0 eV). It has been reported that RuO 2 forms good ohmic contacts on p-GaN [13] and forms good Schottky contacts on n-GaN [12]. We believe RuO 2 should also form good Schottky contacts on our n-ZnO epitaxial layers so that we should be able to effectively suppress the dark current.…”

Section: Resultsmentioning

confidence: 78%

“…In other words, we achieved a photocurrent to dark current contrast ratio of 225. We should be able to significantly improve this contrast ratio by annealing the Ru electrodes in oxygen containing ambient [12,13]. Previously, it has been shown that one can achieve RuO 2 by such annealing.…”

Section: Resultsmentioning

confidence: 99%

“…However, it has also been shown that Au/ZnO and Ag/ZnO Schottky contacts have serious problems at elevated temperatures higher than 330 K [11]. Ruthenium (Ru) metal is an interesting metal that has recently been used as the contact material of wide band gap GaN [12,13]. Ru is a good conductor with superior thermal and chemical stabilities.…”

Section: Introductionmentioning

confidence: 99%

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ZnO MSM photodetectors with Ru contact electrodes

Lin

Chang

et al. 2005

Journal of Crystal Growth

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Section: Resultsmentioning

confidence: 78%

Section: Resultsmentioning

confidence: 99%

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ZnO MSM photodetectors with Ru contact electrodes

Lin

Chang

et al. 2005

Journal of Crystal Growth

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“…In other words, severe inter-diffusion might occur at metal-ZnO interface. Iridium (Ir) is an interesting metal that has been used as stable Schottky contact of wide bandgap GaN [20]- [22]. Ir is a good conductor with superior thermal and chemical stabilities.…”

Section: Introductionmentioning

confidence: 99%

Ir/n-ZnO Schottky Barrier Ultraviolet Photodiodes

Young

2011

IEEE Sensors J.

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ZnO Schottky barrier photodiodes (PDs) with Iridium (Ir) contact electrodes were fabricated in this study. We could reduce the reverse leakage current and improve the performance of ZnO ultraviolet (UV) PDs by using 500 C, O 2 annealing. This could be attributed to the formation of IrO 2 after thermal annealing. With 1 V applied bias, it was found that the reverse current for nonannealed and 500 C, O 2 annealed PDs were 4 46 10 9 and 8 87 10 11 A, respectively. It was also found that we could enhance UV-to-visible rejection ratio, reduce noise level, and enhance the detectivity by high-temperature oxygen annealing.

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“…It is known that IrO x is an electrically conductive oxide with high work function (>5 eV). It has been reported that IrO 2 forms good ohmic contact on p-GaN [16] and good Schottky contact on n-GaN [11]. So, the formation of IrO x should be able to effectively suppress the dark current.…”

mentioning

confidence: 99%

Ir/Pt Schottky contact oxidation for nitride‐based Schottky barrier diodes

Chang

Liu

et al. 2007

Phys. Status Solidi (c)

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We have fabricated Schottky diodes on GaN epitaxial wafer by using Ir/Pt Schottky contacts. After oxidation, the measured leakage current was decreased from 116 nA to 17.8 pA. In other words, the leakage current after annealing in O 2 was shown to be about four orders of magnitude smaller than that before annealing. These improvements may be attributed to IrO x formation of the metal layer, improvement of interface between the Schottky contact and the GaN layer and curing of defects due to oxidation. We also found that the Schottky barrier height and thermal stability after annealing is better than without annealing. 1 Introduction Recently, many people have paid much attention to nitride-based materials due to the wide direct bandgap, high saturation velocity, and high thermal conductivity. Because of the abovementioned properties, the nitride-based materials are promising for applications, not only in optoelectronic devices [1][2][3], but also electronic devices [4,5] such as metal-semiconductor field-effect transistors (MESFETs), and heterojunction field-effect transistors (HFETs). Most of these devices utilize Schottky contacts. However, a substantial leakage current through the Schottky contacts to III-V nitridebased semiconductors has resulted due to the high dislocation density on GaN epitaxial layers. Large leakage current adversely affects operation, power consumption, noise and reliability of the devices. Therefore, Schottky contacts to III-V nitride-based semiconductors with ultralow leakage current are one of the challenges to their use in optoelectronic and electronic devices. To reduce the leakage current and improve the breakdown voltage in Schottky barrier diodes, it is necessary to achieve a high Schottky barrier height at the metal/semiconductor interface. Employing a metal with high work function, such as Pt (5.65 eV) [6], Ni (5.15 eV) [7], or Pd (5.12 eV) [8] is a common method of maximizing the effective Schottky barrier height on GaN layers. However, the majority of these metal films are not stable under high temperature conditions due to inter-diffusion between the metal and the GaN [9]. Iridium (Ir, 5.46 eV) has been predicted to form thermally stable contacts on GaN. In the literature, Ir is often used as the thermally stable Schottky contact material on AlGaN/GaN heterostructure [10]. Although only few studies of oxidized Ir forming Schottky contacts on GaN MSM UV photodetectors have been reported [11], it has also been shown that Ir/Ni can form Schottky contacts on GaN Schottky UV photodiodes with low dark current [12]. Due its properties, Pt is the perfect material that provides a high degree of inertness. However, we know that the strength and durability can be improved by adding a small amount of Ir. Therefore, we used the multi-layer contact with high work function as our contact, including Ir and Pt in our study and compared the experimental results without and with annealing.

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Transparent Ohmic contacts of oxidized Ru and Ir on p-type GaN

Cited by 32 publications

References 18 publications

ZnO MSM photodetectors with Ru contact electrodes

ZnO MSM photodetectors with Ru contact electrodes

Ir/n-ZnO Schottky Barrier Ultraviolet Photodiodes

Ir/Pt Schottky contact oxidation for nitride‐based Schottky barrier diodes

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