Analysis of GaN cleaning procedures

Diale, M.; Auret, F.D.; Berg, N.G. van der; Odendaal, R.Q.; Roos, W.

doi:10.1016/j.apsusc.2004.11.024

Cited by 62 publications

(29 citation statements)

References 17 publications

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“…For above unity has been attributed to interface states due to thin oxide layer between the metal and the semiconductor, including other contaminants, tunneling currents in highly doped semiconductors, image-force lowering of the Schottky barrier in electric field at the interface and generation-recombination currents within the depletion region [2]. Our previous results have shown S and Cl residues onto GaN after cleaning in HCl and (NH 4 ) 2 S using Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) [13]. The work done on GaAs and GaP nitridation has shown anion exchange where a thin layer of Ga-N was formed on each of the materials [14].…”

Section: Diale Fd Auret / Physica B ] (]]]]) ]]]-]]]mentioning

confidence: 99%

Effects of chemical treatment on barrier height and ideality factors of Au/GaN Schottky diodes

Diale

Auret

2009

Physica B: Condensed Matter

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a b s t r a c tWe have studied Au/n-GaN Schottky barrier diodes. GaN surfaces have been prepared by cleaning in HCl and (NH 4 ) 2 S prior to metal deposition. The zero-biased barrier heights and ideality factors obtained from the current-voltage characteristics differ from diode to diode, although all the samples were prepared identically. The statistical analysis for the reverse bias C-V data yielded mean value of (1.357 0.04) eV for Schottky barrier height of HCl treated sample and (1.20 7 0.03) eV for (NH 4 ) 2 S sample, where 9 dots were considered from each cleaning method. It was found that the barrier height values obtained from the C À 2 -V (1.43 eV) and I-V characteristics (0.89 eV) are different from each other by 0.54 eV. The inhomogeneous barrier heights were found to be related to the effect of the high series resistance on diode parameters [1].

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Section: Diale Fd Auret / Physica B ] (]]]]) ]]]-]]]mentioning

confidence: 99%

Effects of chemical treatment on barrier height and ideality factors of Au/GaN Schottky diodes

Diale

Auret

2009

Physica B: Condensed Matter

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“…Alkaline solutions ͑NH 4 OH and KOH͒ are also used to prepare clean surfaces on GaAs, 21,22 GaN, 23 and AlGaN. 24 It has been shown that abrupt GaAs͑001͒ surface is stable against the development of pervasive microroughness in a KOH solution ͑pH ϳ 14͒, while strong acids ͑pH ϳ 0͒ produce deep microroughness.…”

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confidence: 99%

Properties of GaP(001) surfaces chemically treated in NH4OH solution

Morota

Adachi

2006

Journal of Applied Physics

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Chemically cleaned GaP͑001͒ surfaces in 25% NH 4 OH solution have been studied using spectroscopic ellipsometry ͑SE͒, ex situ atomic force microscopy ͑AFM͒, x-ray photoelectron spectroscopy ͑XPS͒, and wettability measurement techniques. The SE data clearly indicate that the solution causes removal of the native oxide film immediately upon immersing the sample. The SE data also indicate that when the native oxide film is completely etch removed, the resulting surface is still roughened. The estimated roughness thickness is ϳ1.2 nm, in excellent agreement with the AFM rms value ͑ϳ1.2 nm͒. The XPS spectra confirm the removal of the native oxide from the GaP surface. The XPS data also suggest a thin oxide overlayer, ϳ0.3 nm thick, on the etch-cleaned GaP surface. The wettability measurements indicate that the as-degreased surface is hydrophobic, while the NH 4 OH-cleaned surface is hydrophilic. This result is in direct contrast to those obtained from acid cleaned surfaces, which are usually hydrophobic. The origin of hydrophilicity may be singular and associated hydroxyl groups bonded on the GaP surface.

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“…For instance, Chang et al 22 used an HCl solution cleaning method but residual Cl was detected on the GaN surface, causing an increase of interface traps. Diale et al 23 used an aqueous solution of (NH 4 ) 2 S to clean the GaN surface, producing low C and O concentration and a low the root mean square (RMS) roughness. Nepal et al 24 compared several GaN surface pretreatments on the Ga-polar face including H 2 O 2 : H 2 SO 4 solution (piranha), HF solution and HCl solution, among which piranha produced the most * Electrochemical Society Active Member.…”

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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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Analysis of GaN cleaning procedures

Cited by 62 publications

References 17 publications

Effects of chemical treatment on barrier height and ideality factors of Au/GaN Schottky diodes

Effects of chemical treatment on barrier height and ideality factors of Au/GaN Schottky diodes

Properties of GaP(001) surfaces chemically treated in NH4OH solution

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

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Analysis of GaN cleaning procedures

Cited by 62 publications

References 17 publications

Effects of chemical treatment on barrier height and ideality factors of Au/GaN Schottky diodes

Effects of chemical treatment on barrier height and ideality factors of Au/GaN Schottky diodes

Properties of GaP(001) surfaces chemically treated in NH4OH solution

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

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