Insulating gallium oxide layer produced by thermal oxidation of gallium‐polar GaN

Hossain, T.; Wei, Daming; Nepal, Neeraj; Garces, N. Y.; Hite, Jennifer K.; Meyer, Harry M.; Eddy, Charles R.; Baker, Troy J.; Mayo, Ashley; Schmitt, Jason; Edgar, James H.

doi:10.1002/pssc.201300659

Cited by 14 publications

(8 citation statements)

References 6 publications

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“…9 These trap states are caused by rough interfaces, incomplete and unsatisfied chemical bonds, and impurities. 10 This paper verifies the effectiveness of an ex situ wet chemical etching of GaN prior to ALD of Al 2 O 3 . Since the insulating dielectric must be deposited and is not produced by thermal oxidation, cleaning prior to the oxide deposition must remove native oxides, carbon, and other contamination while leaving the surface smooth.…”

Section: Introductionsupporting

confidence: 63%

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Effect of GaN surface treatment on Al2O3/n-GaN MOS capacitors

Hossain

Wei

Edgar

et al. 2015

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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The surface preparation for depositing Al 2 O 3 for fabricating Au/Ni/Al 2 O 3 /n-GaN (0001) metal oxide semiconductor (MOS) capacitors was optimized as a step toward realization of high performance GaN MOSFETs. The GaN surface treatments studied included cleaning with piranha (H 2 O 2 :H 2 SO 4 ¼ 1:5), (NH 4 ) 2 S, and 30% HF etches. By several metrics, the MOS capacitor with the piranha-etched GaN had the best characteristics. It had the lowest capacitance-voltage hysteresis, the smoothest Al 2 O 3 surface as determined by atomic force microscopy (0.2 nm surface roughness), the lowest carbon concentration ($0.78%) at the Al 2 O 3 /n-GaN interface (from x-ray photoelectron spectroscopy), and the lowest oxide-trap charge (Q T ¼ 1.6 Â 10 11 cm À2 eV À1

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Section: Introductionsupporting

confidence: 63%

“…In selecting the gate oxide, a band offset larger than 1 eV is needed to suppress leakage currents. 6 In this respect, Al 2 O 3 is an excellent high-j dielectric, due to its high permittivity (8)(9)(10), large bandgap (8.9 eV), and high energy conduction band edge offset with GaN [2.13 eV (Ref.…”

Section: Introductionmentioning

confidence: 99%

Effect of GaN surface treatment on Al2O3/n-GaN MOS capacitors

Hossain

Wei

Edgar

et al. 2015

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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“…6,10,11 However, a metaloxide-semiconductor structure is preferred, as it provides a higher input impedance, larger gate voltage swings, and lower gate leakage currents. 12,13 Aluminum oxide (Al 2 O 3 ) is an excellent gate dielectric for IIInitride based devices due to its large bandgap (7∼9 eV), relatively high dielectric constant (∼9) and high thermal stability (up to 1000…”

mentioning

confidence: 99%

A Comparison of N-Polar () GaN Surface Preparations for the Atomic Layer Deposition of Al₂O₃

Wei

Hossain

Briggs

et al. 2014

ECS J. Solid State Sci. Technol.

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Nitrogen-polar gallium nitride offers several advantages over Ga-polar GaN for high frequency-high power electronic devices, but its processing has not been fully developed. Here we report on a systematic study of the effect of surface pretreatments on N-polar GaN for metal oxide semiconductor capacitors (MOSCAPs). Bulk n-type GaN (0001) substrates were prepared with a variety of treatments including: HF; HCl; base-piranha; H 2 plasma; and no pretreatment for comparison. Then 14nm thick Al 2 O 3 layers were deposited by atomic layer deposition (ALD). Both the original surfaces of GaN and ALD films were characterized by atomic force microscopy (AFM). MOSCAPs were fabricated and characterized by capacitance-voltage (C-V) and current voltage (I-V) measurements. The surface morphology and electrical performance was greatly affected by the pretreatments due to the reactive nature of N-polar GaN. The MOSCAP fabricated on GaN as-received with no additional preparation had the best performance including the smallest hysteresis (0.03V), lowest leakage current density (2.09 × 10 −8 A/cm 2 at +4V) and total trap density (2.47 × 10 10 cm −2 eV −1 ). This was correlated to the smoothest surface morphology (0.23 nm). The wide bandgap semiconductor gallium nitride (GaN) is of great interest not only for optoelectronic devices such as blue LEDs, 1 laser diodes, 2 and UV detectors, but also for highly efficient electronic devices operating at high frequency, temperature and power. After years of development, Ga-polar GaN based high electron mobility transistors (HEMTs) have been demonstrated with excellent performance and high RF output power.3,4 Increasing the maximum frequency by scaling down the GaN HEMT dimensions to reduce electron transit time, establishing control of the contact resistance and capacitive elements are critically important to prevent device delay times and to achieve the best possible device performance.5 Nitrogen-polar GaN has potential advantages over Ga-polar GaN for high-frequency applications due to its low contact resistance and a natural back barrier to improve electron confinement.6-8 For example, an extremely low contact resistance of 23 -μm was reported by Mishra et al. 9 To date, most of the N-polar GaN HEMT devices employ structures with a Schottky barrier as the gate contact. 6,10,11 However, a metaloxide-semiconductor structure is preferred, as it provides a higher input impedance, larger gate voltage swings, and lower gate leakage currents. 12,13 Aluminum oxide (Al 2 O 3 ) is an excellent gate dielectric for IIInitride based devices due to its large bandgap (7∼9 eV), relatively high dielectric constant (∼9) and high thermal stability (up to 1000• C). 14-20 Precise control of this dielectric's thickness is necessary to maintain the aspect ratio between the gate length and the oxide thickness for good high frequency performance. Atomic layer deposition (ALD) offers excellent thickness control for the deposition of such dielectrics, 21 but the initial condition of the substrate surface is crucia...

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“…In recent years, gallium oxide (Ga 2 O 3 ) has drawn increasing attention as a dielectric material owing to its superior dielectric properties such as high dielectric constant (9.9-10.2) [4], high breakdown strength (> 7 MV cm −1 ) [5], and high chemical and thermal stability. Ga 2 O 3 thin-films were successfully obtained on various foreign substrates using various techniques such as sputtering [6], atomic layer deposition [7,8], and oxidation [9,10]. Ga 2 O 3 /GaN MOS structures are of particular interest due to the fact that a few monolayers of native Ga 2 O 3 decorate the GaN surface because of the spontaneous termination of the Ga-atoms with oxygen [11,12], affecting the interface property between the oxide and underlying GaN.…”

Section: Introductionmentioning

confidence: 99%

A study of temperature dependent current–voltage (I–V–T) characteristics in Ni/sol–gel β-Ga2O3/n-GaN structure

Gao

Kaya

Chopdekar

et al. 2018

J Mater Sci: Mater Electron

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β-Ga 2 O 3 thin films were grown on n-type GaN substrates using the sol-gel method. The forward-biased temperature dependent current-voltage (I-V-T) characteristics of Ni/β-Ga 2 O 3 /GaN structure have been investigated in the temperature range of 298-473 K. The apparent barrier height (ap) increased while the ideality factor (n) decreased with the increase in temperature. Such a temperature dependent behavior of ap and n was explained by the inhomogeneity of ap , which obeyed Gaussian distribution with zero-bias mean barrier height (̄B 0) of 1.02 ± 0.02 eV and standard deviation (s0) of 153 ± 0.04 mV. Subsequently, ̄B 0 and Richardson constant A * were obtained from the slope and intercept of the modified Richardson plot as 0.99 ± 0.01 e V and 67.2 A cm −2 K −2 , respectively. The ̄B 0 obtained from the modified Richardson plot was in good agreement with the theoretical value calculated from the work function of Ni and electron affinity of β-Ga 2 O 3. The I-V-T characteristics of Ni/β-Ga 2 O 3 /GaN MOS structures can be successfully explained by the thermionic emission theory with a single Gaussian distribution of the barrier height.

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Insulating gallium oxide layer produced by thermal oxidation of gallium‐polar GaN

Cited by 14 publications

References 6 publications

Effect of GaN surface treatment on Al2O3/n-GaN MOS capacitors

Effect of GaN surface treatment on Al2O3/n-GaN MOS capacitors

A Comparison of N-Polar () GaN Surface Preparations for the Atomic Layer Deposition of Al₂O₃

A study of temperature dependent current–voltage (I–V–T) characteristics in Ni/sol–gel β-Ga2O3/n-GaN structure

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Insulating gallium oxide layer produced by thermal oxidation of gallium‐polar GaN

Cited by 14 publications

References 6 publications

Effect of GaN surface treatment on Al2O3/n-GaN MOS capacitors

Effect of GaN surface treatment on Al2O3/n-GaN MOS capacitors

A Comparison of N-Polar () GaN Surface Preparations for the Atomic Layer Deposition of Al2O3

A study of temperature dependent current–voltage (I–V–T) characteristics in Ni/sol–gel β-Ga2O3/n-GaN structure

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Product

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A Comparison of N-Polar () GaN Surface Preparations for the Atomic Layer Deposition of Al₂O₃