Ohmic Contact to <i>p</i>-Type GaN Enabled by Post-Growth Diffusion of Magnesium

Wang, J.; Lu, Shun; Cai, Wentao; Kumabe, Takeru; Ando, Yoshinobu; Liao, Yaqiang; Honda, Yoshio; Xie, Ya‐Hong; Amano, Hiroshi

doi:10.1109/led.2021.3131057

Cited by 18 publications

(13 citation statements)

References 23 publications

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“…This phenomenon is attributed to several reasons, mainly related to the characteristics of the p-FET: 1) Schottky turn-on behavior of the p-FET and 2) significant field-induced acceptor ionization at high gate overdrives and highly negative drain biases, in particular for the FinFET structure, as explained in Section II-B. Finally, it should be acknowledged that, significant research remains to be done in the co-optimization of this emerging GaN CT in the following: 1) further advancement of various process modules, e.g., ohmic contacts with low contact resistance [44], [45], [46] and low damage gate recess [25], [28]); 2) device and process engineering to achieve a good balance of performance specifications (DC and switching characteristics); and 3) epitaxial structure, to achieve lower channel resistances while ensuring carrier confinement.…”

Section: B Results and Discussionmentioning

confidence: 99%

Highly Scaled GaN Complementary Technology on a Silicon Substrate

Xie

Yuan

Niroula

et al. 2023

IEEE Trans. Electron Devices

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This article reports on the scaling of GaN complementary technology (CT) on a silicon substrate to push its performance limits for circuit-level applications. The highly scaled self-aligned (SA) p-channel FinFET (a fin width of 20 nm) achieved an I D,max of −300 mA/mm and an R ON of 27 •mm, a record for metal organic chemical vapor deposition (MOCVD)-grown III-nitride p-FETs. A systematic study on impact of fin width scaling and recess depth in these transistors was conducted. A new SA scaled n-channel p-GaN-gate FET (n-FET) process, compatible with the p-FinFET, demonstrated enhancement-mode (E-mode) n-FETs (L G = 200 nm, I D,max = 525 mA/mm, and R ON = 2.9 •mm) on the same epitaxial platform. The p-FETs and n-FETs feature competitive performance in their respective categories and, when taken together, offer a leading solution for GaN CT on a silicon substrate.

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Section: B Results and Discussionmentioning

confidence: 99%

Highly Scaled GaN Complementary Technology on a Silicon Substrate

Xie

Yuan

Niroula

et al. 2023

IEEE Trans. Electron Devices

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“…Contacts with transparent conductive oxides such as Sn-doped In 2 O 3 (ITO) and Al-doped ZnO (AZO) have been developed, with AZO being more appealing than ITO as it is more environmentally friendly and cheaper, as well as having better electrical and optical properties . Nonetheless, AZO electrodes directly on p-GaN do not give the best performance, with I–V curves showing nonlinear characteristics or high specific contact resistances (ρ c ). , Hence, different interlayers such as Ni, − Pt, , ITO, , or Ag , have been used for Ohmic contacts to p-GaN.…”

Section: Introductionmentioning

confidence: 99%

Development of Low-Resistance Ohmic Contacts with Bilayer NiO/Al-Doped ZnO Thin Films to p-type GaN

Tlemçani

Mauduit

Bah

et al. 2023

ACS Appl. Mater. Interfaces

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The fabrication of low-resistance and thermally stable Ohmic contacts is essential for the realization of reliable GaN power devices. In the particular case of p-type GaN, a thin Ni/Au bilayer is commonly used for Ohmic contacts. However, Au metal contacts are quite expensive, are incompatible with the complementary metal oxide−semiconductor foundries, and also have poor thermal stability. Thus, seeking an alternative that is affordable and thermally stable is crucial. In the present study, we investigate Au-free Ohmic contact formation on p-type GaN using a bilayer Ni/Al-doped ZnO (AZO) thin film. Careful studies were focused on identifying the role of process parameters such as annealing parameters: temperature, time, and atmosphere in order to obtain an excellent Ohmic contact on p-GaN. Our results show that the contact resistance can be significantly reduced using a Ni/AZO bilayer with a suitable rapid thermal process. We demonstrate that the specific contact resistance for Ni/AZO on p-GaN can reach the lowest value of 1.85 × 10 −4 Ω•cm 2 for a sample with a 5 nm Ni layer annealed at 500 °C in air for 5 min. Our work demonstrates that the bilayer Ni/AZO contact could be suitable for efficient GaN power diodes or transistors.

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“…Region I shows a similar Mg distribution to the MgGaN layer, which is annealed at 800 °C for 5 min in Ref. 26. Therefore, region I is considered to be the MgGaN layer or region strongly affected by the MgGaN layer.…”

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confidence: 96%

“…As a Mg-diffusion source that has these factors, we focus on a GaN/Mg mixture (MgGaN) layer, which is formed by annealing Mg deposited on GaN at about 800 °C in nitrogen atmosphere. 25,26) During this annealing, not only Mg diffuses from the Mg layer into the GaN layer, but Ga also diffuses from the GaN layer into the Mg layer. 25) This suggests that Ga vacancies are introduced into the GaN layer.…”

mentioning

confidence: 99%

“…25) This suggests that Ga vacancies are introduced into the GaN layer. According to Wang et al, most of the Mg that diffused into the GaN layer is not activated, 26) but if the diffusion temperature is further increased, the Mg in the introduced Ga vacancies is likely to be activated; fortunately, the diffusion temperature can be easily increased by depositing a protective film such as AlN on MgGaN. In this paper, we report the Mg diffusion process for p-type GaN formation using MgGaN and the evaluation of Mg-diffused GaN.…”

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confidence: 99%

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Substitutional diffusion of Mg into GaN from GaN/Mg mixture

Itoh¹,

Lu²,

Watanabe³

et al. 2022

Appl. Phys. Express

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We evaluated Mg diffusion into GaN from GaN/Mg mixture. The diffusion depth of Mg increased with diffusion temperature from 1100 °C to 1300 °C, whereas the Mg concentration remained constant at 2–3×10^18 cm^-3 independent of temperature. The estimated activation energy for Mg diffusion was 2.8 eV, from which the substitutional diffusion mechanism was predicted. Mg-diffused GaN samples showed p-type conductivity with a maximum hole mobility of 27.7 cm^2V^-1s^-1, suggesting that substitutional diffusion contributes to Mg activation. This diffusion technique can be used to easily form p-type GaN and has potential as a p-type selective doping technique.

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Ohmic Contact to p-Type GaN Enabled by Post-Growth Diffusion of Magnesium

Cited by 18 publications

References 23 publications

Highly Scaled GaN Complementary Technology on a Silicon Substrate

Highly Scaled GaN Complementary Technology on a Silicon Substrate

Development of Low-Resistance Ohmic Contacts with Bilayer NiO/Al-Doped ZnO Thin Films to p-type GaN

Substitutional diffusion of Mg into GaN from GaN/Mg mixture

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