Comparative study of surface recombination in hexagonal GaN and ZnO surfaces

Onuma, Takeyoshi; Sakai, Naoyuki; Igaki, T.; Yamaguchi, T.; Yamaguchi, Akira; Honda, Toshio

doi:10.1063/1.4752429

Cited by 21 publications

(16 citation statements)

References 33 publications

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“…Thanks to a previously reported technique 47 based on the Monte Carlo simulation shown in Figure 1c . 48 Being 2 orders of magnitude lower than in GaAs, 5 surface recombination was not found to play a role in the fit of EBIC profile at 4 keV and one can therefore neglect this effect in the simulation. A previous study 49 in planar devices also reported another EBIC modeling with negligible surface recombination and ascribed it to the passivation of the surface by the polymerization of the hydrocarbon layer produced during the scanning of the electron beam over the surface of the sample.…”

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confidence: 99%

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Direct Imaging of p–n Junction in Core–Shell GaN Wires

et al. 2014

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While core−shell wire-based devices offer a promising path toward improved optoelectronic applications, their development is hampered by the present uncertainty about essential semiconductor properties along the threedimensional (3D) buried p−n junction. Thanks to a crosssectional approach, scanning electron beam probing techniques were employed here to obtain a nanoscale spatially resolved analysis of GaN core−shell wire p−n junctions grown by catalyst-free metal−organic vapor phase epitaxy on GaN and Si substrates. Both electron beam induced current (EBIC) and secondary electron voltage constrast (VC) were demonstrated to delineate the radial and axial junction existing in the 3D structure. The Mg dopant activation process in p-GaN shell was dynamically controlled by the ebeam exposure conditions and visualized thanks to EBIC mapping. EBIC measurements were shown to yield local minority carrier/exciton diffusion lengths on the p-side (∼57 nm) and the n-side (∼15 nm) as well as depletion width in the range 40−50 nm. Under reverse bias conditions, VC imaging provided electrostatic potential maps in the vicinity of the 3D junction from which acceptor N a and donor N d doping levels were locally determined to be N a = 3 × 10 18 cm −3 and N d = 3.5 × 10 18 cm −3 in both the axial and the radial junction. Results from EBIC and VC are in good agreement. This nanoscale approach provides essential guidance to the further development of core−shell wire devices.

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confidence: 99%

“…Shown in Figure 1c is the spatial distribution of excess carriers generated in GaN material with a 4 keV ebeam as obtained by Monte Carlo simulations of electron trajectories using CASINO sofware v2. 48. 37 This distribution was used to simulate the measured EBIC signal (discussed later).…”

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Direct Imaging of p–n Junction in Core–Shell GaN Wires

et al. 2014

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“…Indeed, Xray photoelectron spectroscopy analysis has exhibited [10] that the spontaneous polarization induces upward band bending toward a Zn-polarity (+c) surface and downward but weaker band bending toward an O-polarity (-c) surface. Accordingly, previous analyses using steady-state and time-resolved photoluminescence (PL) measurements have confirmed [11,12] that the spontaneous polarizationinduced electric field (F spon ) affects the surface recombination in the c-planes of ZnO-based materials.…”

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confidence: 81%

“…The quantitative agreement indicates that the effect of electron-beam reflection on I CL is negligibly small. No significant difference can be found between +c and -c surfaces, though the PL intensity and lifetime have showed distinct dependence on the surface orientation [12]. The carriers, which were generated by energetic electrons, would induce decrease in the band bending in the present CL measurements.…”

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confidence: 94%

Electron‐beam incident‐angle‐ resolved cathodoluminescence studies on bulk ZnO crystals

Onuma

Yamaguchi

Honda

2013

Phys. Status Solidi C

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Electron‐beam incidence‐angle‐resolved cathodoluminescence (IAR‐CL) measurements on ZnO single crystals were demonstrated as an alternative way for the depth‐resolved cathodoluminescence (CL) study by scanning acceleration voltage of the electron‐beam. Incidence‐angle dependent near‐band‐edge CL intensities were well reproduced by analyses considering a radiation pattern, an expansion of the electron‐beam irradiation area, and an internal absorption factors. The quantitative agreement between the experimental and simulated results indicates that the IAR‐CL technique is suitable for practical use in the depth‐resolved CL study of device structures (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…8, which consists of a UV emission located at 378 nm and a green emission band centered at 546 nm. The UV emission is attributed to the near band edge (NBE) emission of ZnO [31][32][33]. The green emission band is originated from ionized oxygen vacancies [34][35][36].…”

Section: Characterization and Measurementsmentioning

confidence: 99%

Band alignment tuned by 3-PPA SAMs interfacial modification to enhance the conversion efficiency of ZnO/ZnS heterostructure quantum dots sensitized solar cells

Yang

Luan

Chen

et al. 2015

J Mater Sci: Mater Electron

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The 3-Phosphonopropionic acid (3-PPA) selfassembled monolayers with a phosphonic acid headgroup and carboxylic acid tailgroups were introduced into the interface of ZnO/ZnS heterostructure by a simple chemical immersion process. Ultraviolet photoemission spectroscopy (UPS) was utilized to determine the variation of band alignment. The UPS results revealed that the 3-PPA can act as buffer layer in ZnO/ZnS heterostructure to lower the energy barrier formed by ZnS. This new energy barrier can not only work efficiently on retarding the back transfer of electrons, but also weaken the blocking effect on the charge injection process, which finally results in the enhancement of photoelectric conversion efficiency.

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Comparative study of surface recombination in hexagonal GaN and ZnO surfaces

Cited by 21 publications

References 33 publications

Direct Imaging of p–n Junction in Core–Shell GaN Wires

Direct Imaging of p–n Junction in Core–Shell GaN Wires

Electron‐beam incident‐angle‐ resolved cathodoluminescence studies on bulk ZnO crystals

Band alignment tuned by 3-PPA SAMs interfacial modification to enhance the conversion efficiency of ZnO/ZnS heterostructure quantum dots sensitized solar cells

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