Nanostructure growth-induced defect formation and band bending at ZnO surfaces

Merz, Tyler A.; Doutt, Daniel R.; Bolton, T.; Dong, Yufeng; Brillson, L. J.

doi:10.1016/j.susc.2010.12.021

Cited by 27 publications

(15 citation statements)

References 15 publications

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“…The sign of the slope change at this energy corresponds to a defect level located 1.1 eV above the valence band [32]. This result agrees with our DRCLS mapping result that defect densities are lower in brighter areas, e.g., region 1.…”

Section: E Defect Energy Levelsupporting

confidence: 90%

Strain and Temperature Dependence of Defect Formation at AlGaN/GaN High-Electron-Mobility Transistors on a Nanometer Scale

Lin

Merz

Doutt

et al. 2012

IEEE Trans. Electron Devices

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Abstract-We use depth-resolved cathodoluminescence spectroscopy (DRCLS), Kelvin probe force microscopy (KPFM), and surface photovoltage spectroscopy (SPS) on a nanometer scale to map the temperature, strain, and defects inside GaN highelectron-mobility transistors. DRCLS maps temperature at localized depths, particularly within the 2-D electron gas region during device operation. KPFM maps surface electric potential across the device, revealing lower potential patches that decrease rapidly with increasing OFF-state stress. CL spectra acquired at these patches exhibit defect emissions that increase with both ONand OFF-state stresses and that increase with decreasing surface potential. SPS also reveals features of deep level gap states generated after device operation that reduce near-band-edge emission and increase surface band bending. Our nanoscale measurements are consistent with defect generation by inverse piezoelectric fieldinduced stress at the gate edge on the drain side at high voltage.Index Terms-AlGaN/GaN high-electron-mobility transistor (HEMT), defect characterization, depth-resolved cathodoluminescence spectroscopy (DRCLS), HEMT, Kelvin force probe microscopy, strain mapping, surface photovoltage spectroscopy (SPS), temperature mapping.

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Section: E Defect Energy Levelsupporting

confidence: 90%

Strain and Temperature Dependence of Defect Formation at AlGaN/GaN High-Electron-Mobility Transistors on a Nanometer Scale

Lin

Merz

Doutt

et al. 2012

IEEE Trans. Electron Devices

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“…To investigate defect energy positions and densities after polishing and HF etching, we used SPS employing an atomic force microscope (AFM) combined with Kelvin probe force microscopy (KPFM) to measure surface potential with nanometer scale spatial resolution and as a function of incident photon energy. [43][44][45] SPS monitors changes in surface electric potential with illumination as incident photon energy h sweeps from low to above-band-gap energies. The corresponding contact potential difference (CPD) between the illuminated surface and the KPFM tip varies with h as n-type semiconductor band bending increases (decreases) with electron filling (emptying) of near-surface states at characteristic threshold energies.…”

mentioning

confidence: 99%

Characterization of polishing induced defects and hydrofluoric acid passivation effect in ZnO

Zhang

Quemener

Lin

et al. 2013

Applied Physics Letters

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We used depth-resolved cathodoluminescence spectroscopy and transient photovoltage spectroscopy (T-SPS) measurements to study the spatial distributions and densities of native point defects in bulk ZnO samples subjected to mechanical polishing and how the defects change with hydrofluoric acid (HF) etching. Mechanical polishing produces Zn vacancy-related defects that deplete free carriers at depths extending to 300-500 nm, while HF etching removes/passivates these defects as well as bulk oxygen vacancy-related defects, restoring the charge carriers below the etched surface. T-SPS defect density changes with polishing/etching correlate closely with deep level transient spectroscopy densities, demonstrating the applicability of T-SPS as a non-contact quantitative defect density measurement technique. V

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“…They observed an interesting spontaneous growth of nanostructures on ZnO polar surfaces during long-term air exposure due to diffusion of Zn atoms, which resulted in the creation of Zn vacancies. 22 During long-term air-exposure, the increasing surface adsorption, as well as the increasing concentration of near-surface Zn vacancies enhances the surface-mediated nonradiative and DL recombination, thus, decreasing the UV emission efficiency of the device. Whereas, an opposite situation occurs in the desorption process.…”

mentioning

confidence: 99%

Effect of oxygen-related surface adsorption on the efficiency and stability of ZnO nanorod array ultraviolet light-emitting diodes

Liu

et al. 2012

Applied Physics Letters

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Ultraviolet light-emitting diodes using MgZnO-coated and bare ZnO nanorod arrays as active layers were manufactured. Both types were exposed to ambient air over a 1-yr period to assess their stability. By monitoring the electroluminescence evolution with air-exposure time and comparing the changes of electroluminescence and x-ray photoelectron spectra before and after vacuum desorption, it is concluded that surface-adsorbed O2 and OH− species, as acceptor and donor surface states, quench ultraviolet electroluminescence, and favor undesirable surface-mediated nonradiative and deep-level recombination. The MgZnO coating prevents surface adsorption, and so the coated nanorod device shows higher efficiency and stability than the uncoated one.

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Nanostructure growth-induced defect formation and band bending at ZnO surfaces

Cited by 27 publications

References 15 publications

Strain and Temperature Dependence of Defect Formation at AlGaN/GaN High-Electron-Mobility Transistors on a Nanometer Scale

Strain and Temperature Dependence of Defect Formation at AlGaN/GaN High-Electron-Mobility Transistors on a Nanometer Scale

Characterization of polishing induced defects and hydrofluoric acid passivation effect in ZnO

Effect of oxygen-related surface adsorption on the efficiency and stability of ZnO nanorod array ultraviolet light-emitting diodes

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