Evolution of Electrically Active Defects in n‐GaN During Heat Treatment Typical for Ohmic Contact Formation

Boturchuk, Ievgen; Scheffler, L.; Larsen, A. Nylandsted; Julsgaard, Brian

doi:10.1002/pssa.201700516

Cited by 9 publications

(10 citation statements)

References 30 publications

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“…Nitrogen interstitials have been reported to introduce trap states between EC -1.2 eV and EC -0.76 eV [321]- [328], with average preferential energy positioning at EC -1.02 eV, EC -0.89 eV and EC -0.79 eV. The former and the latter levels have also been tentatively associated with an extended defect in [326]. Among nitrogen-related native defects, nitrogen interstitials exhibit the highest activation energy, allowing them to act both as traps or recombination centers.…”

Section: Native Defectsmentioning

confidence: 99%

“…Nitrogen antisite defects are assumed to form a mini-band of levels between EC -0.66 eV and EC -0.5 eV [322], [326], [329]- [339]. None of the aforementioned reports suggests a direct correlation between the levels associated to nitrogen antisite defects and extended defects.…”

Section: Native Defectsmentioning

confidence: 99%

“…Nitrogen vacancies represent the most commonly observed type of native defect in GaN, with more than 40 records in 25 different scientific publications [322], [326], [329]- [339]. The associated trap states are preferentially positioned in the EC -0.27 eV to EC -0.089 eV range, with most of the occurrences belonging to the mini-band at EC -(0.24 ± 0.003) eV identifying the typical level associated to nitrogen vacancies in GaN.…”

Section: Native Defectsmentioning

confidence: 99%

“…Trap states related to extended defects have been found to cover a wide and non-continuous portion of the upper part of the GaN bandgap, ranging from EC -1.118 eV to EC -0.24 eV [323], [326], [330], [333], [335], [341], [348], [352], [360], [361]. Interestingly, the upper group of levels, scattered from EC -0.27 eV to EC -0.17 eV, covers the same range of activation energies exhibited by VN-related defects.…”

Section: Native Defectsmentioning

confidence: 99%

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GaN-based power devices: Physics, reliability, and perspectives

Meneghini

Santi

Abid

et al. 2021

Journal of Applied Physics

346

126

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Over the last decade, gallium nitride has emerged as an excellent material for the fabrication of power devices. Among the semiconductors for which power devices are already available on the market, GaN has the widest energy gap, the largest critical field, the highest saturation velocity, thus representing an excellent material for the fabrication of high speed/high voltage components.The presence of spontaneous and piezoelectric polarization allows to create a 2-dimensional electron gas, with high mobility and large channel density, in absence of any doping, thanks to the use of AlGaN/GaN heterostructures. This contributes to minimize resistive losses; at the same time, for GaN transistors switching losses are very low, thanks to the small parasitic capacitances and switching charges. Device scaling and monolithic integration enable high frequency operation, with consequent advantages in terms of miniaturization.For high power/high voltage operation, vertical device architectures are being proposed and investigated, and 3-dimensional structuresfin-shaped, trench-structured, nanowire-basedare demonstrating a great potential. Contrary to silicon, GaN is a relatively young material: trapping and degradation processes must be understood and described in detail, with the aim of optimizing device stability and reliability. This tutorial paper describes the physics, technology and reliability of GaN-based power devices: in the first part of the article, starting from a discussion of the main properties of the material, the characteristics of lateral and vertical GaN transistors are discussed in detail, to provide guidance in this complex and interesting field. The second part of the paper focuses on trapping and reliability aspects: the physical origin of traps in GaN, and the main degradation mechanisms are discussed in detail. The wide set of referenced papers and the insight on the most relevant aspects gives the reader a comprehensive overview on present and next-generation GaN electronics. IntroductionOver the past decade, gallium nitride has emerged as an excellent material for the fabrication of power semiconductor devices. Thanks to the unique properties of GaN, diodes and transistors based on this material have excellent performance, compared to their silicon counterparts, and are expected to find wide application in the next-generation power converters. Owing to the flexibility and the energy efficiency of GaN-based power converters, the interest towards this technology is rapidly growing: the aim of this tutorial is to review the most relevant physical properties, the operating principles, the fabrication parameters, and the stability/reliability issues of GaN-based power transistors. For introductory purposes, we start summarizing the physical reasons why GaN transistors achieve a much better performance than the corresponding silicon devices, to help the reader understanding the unique advantages of this technology.The properties of GaN devices allow the fabrication of high-efficiency (near or above 99 %)...

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Section: Native Defectsmentioning

confidence: 99%

Section: Native Defectsmentioning

confidence: 99%

Section: Native Defectsmentioning

confidence: 99%

Section: Native Defectsmentioning

confidence: 99%

See 2 more Smart Citations

GaN-based power devices: Physics, reliability, and perspectives

Meneghini

Santi

Abid

et al. 2021

Journal of Applied Physics

346

126

View full text Add to dashboard Cite

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“…However, annealing temperature above 800 • C is normally required for this type of contact, resulting in poor edge acuity, due to the diffusion of melted Al, and hampering downscaling of the drain-and source-to-gate distance. Moreover, high annealing temperature may degrade the GaN crystal structure, increase traps [12], and reduce 2DEG density due to strain relaxation [13].…”

Section: Introductionmentioning

confidence: 99%

Structural investigation of ultra-low resistance deeply recessed sidewall ohmic contacts for AlGaN/GaN HEMTs based on Ti/Al/Ti-metallization

Chen,

Persson,

Darakchieva

et al. 2023

Semicond. Sci. Technol.

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This study presents a novel approach to forming low-resistance ohmic contacts for AlGaN/GaN HEMTs. The optimized contacts exhibit an outstanding contact resistance of approximately 0.15 Ω·mm. This is achieved by firstly recessing the barrier of the heterostructure to a depth beyond the channel. In this way, the channel region is exposed on the sidewall of the recess. The coverage of the Ti/Al/Ti ohmic metalization on the sidewall is ensured through tilting of the sample during evaporation. The annealing process is performed at a low temperature of 550 °C. The approach does not require precise control of the recess etching. Furthermore, the method is directly applicable to most barrier designs in terms of thickness and Al-concentration. The impact of recessed sidewall angle, thickness and ratio of Ti and Al layers, and the annealing procedure are investigated. Structural and chemical analyses of the interface between the ohmic contacts and epi-structure indicate the formation of ohmic contacts by the extraction of nitrogen from the epi-structure. The approach is demonstrated on HEMT-structures with two different barrier designs in terms of Al-concentration and barrier thickness. The study demonstrate large process window in regard to recess depth and duration of the annealing as well as high uniformity of the contact resistance across the samples, rendering the approach highly suitable for industrial production processes.

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