Effect of sodium sulfide treatment on band bending in GaAs

Besser, R.S.; Helms, C. R.

doi:10.1063/1.99024

Cited by 72 publications

(31 citation statements)

References 5 publications

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“…Initial work involving chemical treatments focused on GaAs surfaces passivated with inorganic sulfides, such as Na 2 S and (NH 4 ͒ 2 S. [1][2][3][4][5][6] More recently, passivation has been successfully achieved with the use of selenium sulfide 7 and other group VI sources. [8][9][10] The success of these inorganic sulfides has led some workers to investigate organic thiols, 11 most notably octadecylthiol ͑ODT͒, which forms a selfassembled monolayer on the surface of GaAs.…”

Section: Department Of Chemistry and Materials Research Laboratory Umentioning

confidence: 99%

Near-surface electronic structure in GaAs (100) modified with self-assembled monolayers of octadecylthiol

Dorsten

Maslar

Bohn

1995

Applied Physics Letters

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Passivation of the GaAs (100) surface by self-assembled monolayers of octadecylthiol (ODT) has been studied using inelastic light scattering as a probe of the near-surface electronic structure. Application of the ODT self-assembled monolayers reduces the width of the depletion region at the surface of GaAs resulting in a reduction of the surface band bending, and the electron scattering time is increased as well. The ODT passivated surfaces are more stable to environmental degradation, over time and under temperature stress, than inorganic sulfide treated surfaces which have been reported. Organic thiol passivation may provide an attractive alternative to inorganic sulfide protocols for reduction of surface recombination velocities in III–V devices.

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Section: Department Of Chemistry and Materials Research Laboratory Umentioning

confidence: 99%

Near-surface electronic structure in GaAs (100) modified with self-assembled monolayers of octadecylthiol

Dorsten

Maslar

Bohn

1995

Applied Physics Letters

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“…The sulfur-oxygen stretching vibration of sulfate, SO 4 2 -and sulfite, SO 3 2 -ions occur in the region of 1140-1170 cm-1 and 950-1000 cm-1 , respectively, while those of a thiosulfate ion, S2032-, occurs in the regions of 1050-1150 cm"1 and 950-1050 cm-1 [33,34]. It is likely that the broad bands observed in these regions in the spectra resulted from a combination of these sulfur-oxygen containing compounds on the surface.…”

Section: Infrared Resultsmentioning

confidence: 99%

“…The sulfides used in the treatments includes gases, such as H 2 S, and liquids, such as Na 2 S.9H 2 0 and (NH 4 ) 2 S solutions. These treatments have been shown to result in improvement in the GaAs surface electronic properties, including low surface recombination velocity [11, low surface state density [2,3], and Fermi level shifting or unpinning [4][5][6]. In addition, enhanced performance in heterojunction bipolar transistors (HBTs) [7,81, metal-insulator-semiconductor (MIS) structures [91, solar cells [6,10], laser diodes [11,12], and p-n junction diodes [3] have all been observed.…”

Section: Introductionmentioning

confidence: 99%

Sulfidation and Post-Sulfidatton Reactions on Gallium Arsenide

Yota

Burrows

1992

MRS Proc.

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Chemical treatment of GaAs with sulfur-containing compounds has been shown to improve GaAs surface electronic properties. There is still considerable controversy, however, regarding the chemical nature of the surface film which results from the sulfidation, and of the basis of the electronic improvement and of the decay in the improved electronic properties with time. We have investigated the surface chemistry of the chemical sulfidation treatment of GaAs with Na 2 S.9H 2 O and (NH[ 4 ) 2 S. Using surface infrared reflection spectroscopy (SIRS) and x-ray photoelectron spectroscopy (XPS), we have studied the GaAs surface and its behavior with time after such treatments. Results show that both of these sulfidation treatments removed the chemical oxide of GaAs, leaving behind a thin film on the surface. XPS results show that the Ga-O and As-O peaks were removed after treatment and that As-S and no Ga-S peaks were formed. Infrared results show that the film deposited after Na 2 S.9H 2 0 treatment slowly reacted in air to form sodium carbonate and rhombic sulfur. In addition, this film contains compounds with sulfur-oxygen bonds, which most likely were arsenic sulfate, sulfite, and thiosulfate salts. The film deposited on the (NH 4 ) 2 Streated GaAs surface was identified as ammonium thiosulfate and slowly decomposed with time. Rinsing with water removed the thin film formed after either sulfidation treatment.

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“…For N-face n-GaN, the exact reason why the sulfide passivation causes the surface Fermi level to shift toward the conductionband edge is not clear at this moment. Offsey et al, 23 investigating the surface characteristics of sulfur-passivated ͑001͒ n-GaAs by photochemistry, and Besser and Helms, 24 investigating the effect of sulfide treatment on the band-bending behaviors of GaAs:Si by PL, reported that the treatments resulted in the unpinning of the surface Fermi level by reducing the surface state density, leading to a reduction of the band bending. Thus, the surface Fermi-level shift observed in our passivated sample might also be explained in terms of the reduction in the surface state density, reducing the band-bending and so the surface barrier heights.…”

Section: H276mentioning

confidence: 98%

Electrical Properties of Ti/Al Ohmic Contacts to Sulfur-Passivated N-Face n-Type GaN for Vertical-Structure Light-Emitting Diodes

Jung

Seong

Kim

et al. 2009

Electrochem. Solid-State Lett.

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We investigate the electrical properties of Ti/Al ohmic contacts on ͑NH 4 ͒ 2 S x -passivated N-face n-GaN:Si ͑4.2 ϫ 10 18 cm −3 ͒ grown by molecular beam epitaxy. It is shown that the passivation results in an increase in the photoluminescence intensity of n-GaN. Current-voltage ͑I-V͒ measurements show that the passivated samples experience a slight degradation in the electrical properties upon annealing at 300°C, while the untreated samples show some improvement although still nonohmic. Based on the I-V and X-ray photoemission spectroscopy results, we describe the possible mechanisms for the passivation and annealing dependence of the electrical properties of the Ti/Al contacts to the N-face n-GaN.For the realization of solid-state lighting, the fabrication of high performance GaN-based white light-emitting diodes ͑LEDs͒ is crucial. In this connection, vertical-structure LEDs, which can allow high external quantum efficiency, have been widely investigated. 1,2 For example, Wang et al., 2 investigating the electrical properties of vertical GaN-based LEDs fabricated by Ni electroplating and laser lift-off techniques, reported that the n-type side-up vertical LEDs produced much higher output power as compared to conventional top-emission LEDs. Unlike top-emission LEDs, vertical LEDs require the formation of high quality ohmic contacts to both N-face nand p-GaN. 2-5 Ohmic contacts to Ga-face n-GaN can be easily formed using Ti-or V-based schemes. 6-10 It was, however, shown that the formation of ohmic contacts to N-face n-GaN was difficult. [3][4][5] This was attributed to the absence of polarizationinduced two-dimensional electron gas ͑2DEG͒ formed at the AlN/ GaN interface due to the opposite directions of spontaneous polarization built from bulk to surface. 11 However, Jang et al. 5 used a 5 nm thick Pd interlayer to facilitate the formation of interfacial AlN, which played an important role in improving the electrical properties of Ti/Al contacts to N-face n-GaN when annealed at temperatures above 400°C.For Ga-face n-GaN, sulfur passivation was widely performed to produce low resistance n-type ohmic contacts. 9,12,13 For example, Lee et al. 9 reported that nonalloyed Ti/Al contacts to ͑NH 4 ͒ 2 S x -treated n-GaN exhibited ohmic behavior with a contact resistivity of ϳ10 −5 ⍀ cm 2 . Song et al. 14 also showed that nonalloyed Ti/Al contacts yielded a contact resistivity of ϳ10 −4 ⍀ cm 2 when surface-treated by a CH 3 CSNH 2 solution. In this work, we passivated N-face n-GaN using an ͑NH 4 ͒ 2 S x solution to modify the surface property and form low resistance Ti/Al ohmic contacts to N-face n-GaN. It is shown that the sulfur passivation causes an increase in photoluminescence ͑PL͒ intensity of n-GaN. It is also shown that the passivated contacts show better electrical behaviors than untreated samples before and after annealing at 300°C. Molecular beam epitaxy ͑MBE͒ was used to grow a 35 nm thick GaN buffer layer on a sapphire substrate, which was followed by the growth of ͑ϳ1 m thick͒ N-face n-type GaN:Si layers...

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Effect of sodium sulfide treatment on band bending in GaAs

Cited by 72 publications

References 5 publications

Near-surface electronic structure in GaAs (100) modified with self-assembled monolayers of octadecylthiol

Near-surface electronic structure in GaAs (100) modified with self-assembled monolayers of octadecylthiol

Sulfidation and Post-Sulfidatton Reactions on Gallium Arsenide

Electrical Properties of Ti/Al Ohmic Contacts to Sulfur-Passivated N-Face n-Type GaN for Vertical-Structure Light-Emitting Diodes

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