Polarization Effects of GaN and AlGaN: Polarization Bound Charge, Band Bending, and Electronic Surface States

Eller, Brianna S.; Yang, Jyh‐Chin; Nemanich, R. J.

doi:10.1007/s11664-014-3383-z

Cited by 50 publications

(24 citation statements)

References 55 publications

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“…During these processes, the upward band bending of Ga-and N-face GaN increased, which may indicate the passivation of donor-like N-vacancy related defect states. The oxygen coverage was determined from XPS measurements, 13,20,39 which are summarized in Table V. After NH 4 OH cleaning, the oxygen coverage on Ga-and N-face GaN was 3.4 6 0.3 and 3.1 6 0.4 monolayers (ML), respectively.…”

Section: A Surface Composition and Oxygen Coveragementioning

confidence: 99%

“…After in-situ NH 3 plasma treatment, the oxygen coverage decreased to $1.0 ML on both surfaces. Bermudez 39 reported a study concerning oxygen chemisorption on Gaface GaN and suggested O was bonded to Ga or N in a direction more nearly along the c axis. 39 Elsner et al 40 reported a theoretical calculation regarding O 2 chemisorption on Gaand N-face GaN.…”

Section: A Surface Composition and Oxygen Coveragementioning

confidence: 99%

“…Bermudez 39 reported a study concerning oxygen chemisorption on Gaface GaN and suggested O was bonded to Ga or N in a direction more nearly along the c axis. 39 Elsner et al 40 reported a theoretical calculation regarding O 2 chemisorption on Gaand N-face GaN. For ideal Ga-face GaN, stable oxygen coverage was $0.375 ML, which could increase to 1 ML for oxygen rich conditions (i.e., where the chemical potential of O is equal to that of O 2 ).…”

Section: A Surface Composition and Oxygen Coveragementioning

confidence: 99%

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Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

Yang

Eller

Nemanich

2014

Journal of Applied Physics

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The effects of surface pretreatment, dielectric growth, and post deposition annealing on interface electronic structure and polarization charge compensation of Ga-and N-face bulk GaN were investigated. The cleaning process consisted of an ex-situ wet chemical NH 4 OH treatment and an in-situ elevated temperature NH 3 plasma process to remove carbon contamination, reduce oxygen coverage, and potentially passivate N-vacancy related defects. After the cleaning process, carbon contamination decreased below the x-ray photoemission spectroscopy detection limit, and the oxygen coverage stabilized at $1 monolayer on both Ga-and N-face GaN. In addition, Ga-and N-face GaN had an upward band bending of 0.8 6 0.1 eV and 0.6 6 0.1 eV, respectively, which suggested the net charge of the surface states and polarization bound charge was similar on Ga-and N-face GaN. Furthermore, three dielectrics (HfO 2 , Al 2 O 3 , and SiO 2 ) were prepared by plasma-enhanced atomic layer deposition on Ga-or N-face GaN and annealed in N 2 ambient to investigate the effect of the polarization charge on the interface electronic structure and band offsets. The respective valence band offsets of HfO 2 , Al 2 O 3 , and SiO 2 with respect to Ga-and N-face GaN were 1.4 6 0.1, 2.0 6 0.1, and 3.2 6 0.1 eV, regardless of dielectric thickness. The corresponding conduction band offsets were 1.0 6 0.1, 1.3 6 0.1, and 2.3 6 0.1 eV, respectively. Experimental band offset results were consistent with theoretical calculations based on the charge neutrality level model. The trend of band offsets for dielectric/GaN interfaces was related to the band gap and/or the electronic part of the dielectric constant. The effect of polarization charge on band offset was apparently screened by the dielectric-GaN interface states. V C 2014 AIP Publishing LLC.

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Section: A Surface Composition and Oxygen Coveragementioning

confidence: 99%

Section: A Surface Composition and Oxygen Coveragementioning

confidence: 99%

Section: A Surface Composition and Oxygen Coveragementioning

confidence: 99%

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Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

Yang

Eller

Nemanich

2014

Journal of Applied Physics

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“…Recently, Eller et al have investigated the influence of polarization of GaN and AlGaN on the surface band bending and the electronic surface states. 27 They suggest nitrogen vacancies or gallium dangling bonds as the surface states responsible for the observed Fermi level pinning.…”

Section: Q Jxmentioning

confidence: 99%

“…Our observation that the surface defect states are passivated to a large extent upon oxidation is in agreement with Eller et al, who suggested gallium dangling bonds as the origin of surface states. 27 In summary, we have investigated the electrochemical properties of MOCVD grown n-type GaN in aqueous electrolyte. Cyclic voltammetry and impedance spectroscopy measurements were performed over a wide range of potentials and frequencies.…”

Section: Q Jxmentioning

confidence: 99%

GaN surface states investigated by electrochemical studies

Winnerl

Garrido

Stutzmann

2017

Applied Physics Letters

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We present a systematic study of electrochemically active surface states on MOCVD-grown n-type GaN in aqueous electrolytes using cyclic voltammetry and impedance spectroscopy over a wide range of potentials and frequencies. In order to alter the surface states, the GaN samples are either etched or oxidized, and the influence of the surface treatment on the defect-mediated charge transfer to the electrolyte is investigated. Etching in HCl removes substoichiometric GaO x , and leads to a pronounced density of electrochemically active surface states. Oxidation effectively removes these surface states. Published by AIP Publishing. Recently, group-III nitride materials have attracted considerable interest in fields such as photo-electrochemistry and photocatalysis due to the favorable energy position of their band edges with respect to the redox levels of relevant species in liquid electrolytes. [1][2][3][4][5][6] The flexibility in doping III-nitrides in a controlled way enables the deterministic generation of either holes (for n-type doping) or electrons (for p-type doping) at the surface under illumination to selectively drive oxidation or reduction reactions, respectively. The presence of electronic defect states directly at or close to the semiconductor surface is known to influence charge transfer at semiconductor electrodes. Such electronically active surface defects, e.g., are responsible for surface band bending determining the separation of photo-excited charge carriers and laterally inhomogeneous charging of the surface due to local charge trapping. For a quantitative analysis of the influence of surface states on electrochemical processes and Schottky diodes, it is important to understand the mechanisms governing charge transfer across the GaN surface. In a previous work, 7 we have combined the contact potential difference (CPD) and photoconductivity measurements to investigate electronic processes at or close to illuminated GaN surfaces. We could show that localized surface defect states play a crucial role in the kinetics of photo-generated charges. Sachsenhauser et al. have investigated the charge transfer across the n-type SiC/electrolyte interface. 8 They performed cyclic voltammetry and impedance spectroscopy measurements over a wide range of potentials and frequencies. Adding the ferricyanide/ferrocyanide redox couple to the electrolyte made it possible to reveal the contribution of surface states to the charge transfer and determine the energy distribution of the surface states. In this work, we have investigated whether or not electrically active states located in the GaN band gap are also involved in the charge transfer to an electrolyte. To this end, we have systematically studied the n-type GaN grown by metal-organic chemical vapor deposition (MOCVD) in aqueous electrolytes using cyclic voltammetry and impedance spectroscopy. Different surface treatments are applied in order to alter the surface states and investigate the influence of these on the details of defectmediated charge transfer.(000...

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Annealing‐Free Ohmic Contacts to n‐Type GaN via Hydrogen Plasma‐Assisted Atomic Layer Deposition of Sub‐Nanometer AlO_x

Christis,

Henning,

Bartl

et al. 2023

Adv Materials Inter

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A plasma‐assisted atomic layer deposition (PE‐ALD) process is reported for creating ohmic contacts to n‐type GaN that combines native oxide reduction, near‐surface doping, and encapsulation of GaN in a single processing step, thereby eliminating the need for both wet chemical etching of the native oxide before metallization and thermal annealing after contact formation. Repeated ALD cycling of trimethyl aluminum (TMA) and high‐intensity hydrogen (H2) plasma results in the deposition of a sub‐nanometer‐thin (≈8 Å) AlOx layer via the partial transformation of the GaN surface oxide into AlOx. Hydrogen plasma‐induced nitrogen vacancies in the near‐surface region of GaN serve as shallow donors, promoting efficient out‐of‐plane electrical transport. Subsequent metallization with a Ti/Al/Ti/Au stack results in low contact resistance, ohmic behavior, and smooth morphology without requiring annealing. This electrical contracting approach thus meets the thermal budget requirements for Si‐based complementary metal–oxide–semiconductor structures and can facilitate the design and fabrication of advanced GaN‐on‐Si heterodevices.

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Polarization Effects of GaN and AlGaN: Polarization Bound Charge, Band Bending, and Electronic Surface States

Cited by 50 publications

References 55 publications

Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

GaN surface states investigated by electrochemical studies

Annealing‐Free Ohmic Contacts to n‐Type GaN via Hydrogen Plasma‐Assisted Atomic Layer Deposition of Sub‐Nanometer AlO_x

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Polarization Effects of GaN and AlGaN: Polarization Bound Charge, Band Bending, and Electronic Surface States

Cited by 50 publications

References 55 publications

Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

GaN surface states investigated by electrochemical studies

Annealing‐Free Ohmic Contacts to n‐Type GaN via Hydrogen Plasma‐Assisted Atomic Layer Deposition of Sub‐Nanometer AlOx

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Product

Resources

About

Annealing‐Free Ohmic Contacts to n‐Type GaN via Hydrogen Plasma‐Assisted Atomic Layer Deposition of Sub‐Nanometer AlO_x