Transient photovoltage in GaN as measured by atomic force microscope tip

Reshchikov, M. A.; Sabuktagin, S.; Johnstone, D.; Morkoç̌, H.

doi:10.1063/1.1774245

Cited by 40 publications

(40 citation statements)

References 22 publications

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“…44,45 In the case of GaN there are recent reports on the presence of a surface potential on the order of 1 eV on the n-GaN surface, independent of the growth technique. [46][47][48] This potential is induced by surface states, uncompensated polarization charges, intrinsic oxideinterface states and/or adsorbed impurities that can create deep levels in the band gap. Theoretically there are empty surface states about 0.6 eV below the conduction band edge on a clean c-plane Ga-face GaN surface.…”

Section: E Broad Background In the 340-346 Ev Regionmentioning

confidence: 99%

Transient photoluminescence of shallow donor bound excitons in GaN

et al. 2010

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We present a detailed study of photoluminescence transients for neutral donor bound excitons ͑DBEs͒ in GaN, notably the O N donor DBE at 3.4714 eV and the Si Ga DBE at 3.4723 eV. The studied samples are thick strain free nominally undoped bulk GaN samples, with a spectroscopic linewidth Ͻ0.5 meV at 2 K. The photoluminescence ͑PL͒ decay curves for these no-phonon ͑NP͒ lines are strongly nonexponential, and do not allow a proper assessment of the characteristic BE decay time. The decay of the LO-phonon replicas as well as the so-called two-electron transitions ͑TETs͒ at lower energies show a nicely exponential behavior, and allow extraction of DBE decay times of about 1.1 ns for the Si DBE and 1.8 ns for the O DBE, respectively. The initial nonexponential decay behavior of the NP lines has been studied in both the common front surface excitation-detection mode and with detection in transmission through the sample. This initial decay is explained as related to scattering processes in the near surface region, involving the DBEs and free excitons ͑FEs͒. Light scattering processes may also contribute to this complex decay shape. The DBE-LO-phonon decay does not discriminate between the O and Si DBEs because of spectral overlap involving different LO modes. The TET decays at 2 K are very different for transitions related to the DBE ground state and DBE excited states ͑going to p-like donor final states͒, for T Ͼ 10 K thermalization between the DBE ground state and DBE excited states produces a common decay time. Thermalization between free and bound excitons appears to occur above about 20 K, when the DBE decay follows the FE decay. A simple two-level modeling of exciton capture and recombination for the PL decay curves of the FE and the DBEs, as commonly used in the literature, is shown to be generally inadequate. A broad PL background in the TET spectral region is suggested to be related to a radiative Auger process, where the DBEs recombine while leaving the donors ionized.

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Section: E Broad Background In the 340-346 Ev Regionmentioning

confidence: 99%

Transient photoluminescence of shallow donor bound excitons in GaN

et al. 2010

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“…2(a) that in case of weak excitations (small ∆Φ(0)) the analytical expression (4) is a good approximation. Note that nearly the same shape of the ∆Φ (t) dependence can be obtained by substantial varying of the parameter C n with a moderate adjustment of Φ [10]. …”

Section: Modelmentioning

confidence: 92%

“…A substantial part of the holes are swept towards the surface by strong near-surface electric field and captured by surface states, resulting in a reduction of the band bending. In the simplest approximation [3,10] the restoration of the charge equilibrium after light is turned off is dictated by thermionic transfer of free electrons from the bulk to the surface states over the barrier; only acceptor-like surface states located below the Fermi level (with the density n s ) participate in the photovoltage transients. After the surface states are partially or completely filled with photogenerated holes and the light is off, the dynamics of the recombination is determined by the following rate equation…”

Section: Modelmentioning

confidence: 99%

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Transient photovoltage in GaN

Reshchikov

Sabuktagin

Johnstone

et al. 2005

phys. stat. sol. (c)

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We studied restoration of the band bending at the surface of undoped GaN layers after illumination with pulses of the above-bandgap light. The absolute value of band bending and transients of the photovoltage were measured with an atomic force microscope in the surface potential mode (Kelvin probe method). The photovoltage transients following very weak excitation with a single pulse of light could be well fitted within a simple phenomenological model accounting for charging of the acceptor-like surface states by free electrons after the light pulse. Photo-induced desorption of ions at the surface and recharging of a surface oxide layer may also affect the value and transients of the photovoltage, particularly if the illumination is prolonged.

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“…[11][12][13] The large qV S dark is usually responsible for high SPV signal and long decay time whereas large r is responsible for short decay time. 13 It should be noted that the interface properties in photodetecting structures can be properly modified by a suitable passivation for improving photo-responses, as it was reported by Liu and Kim 14 for ZnO-based UV photodetectors.…”

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confidence: 99%

High-temperature ultraviolet detection based on surface photovoltage effect in SiN passivated n-GaN films

Matys

Adamowicz

Żytkiewicz

et al. 2016

Applied Physics Letters

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We investigated the surface photovoltage (SPV) effect in n-GaN layers passivated with various insulators, i.e., Al2O3, SiO2, and SiN for ultraviolet (UV) light detection. We revealed that SPV in SiN/GaN shows markedly different behaviour than in oxide/GaN, i.e., the photo-signal exhibited very fast response (1 s) and recovery (2 s) times, contrary to oxide/GaN, and it was thermally stable up to 523 K. Furthermore, SPV spectra for SiN/GaN showed a sharp cut-off edge directly corresponding to the GaN band gap. We explained these results in terms of the different band structure of SiN/GaN and oxide/GaN junctions. All the observed properties of SPV response from SiN/GaN indicate that this relatively simple system can be applied to sensitive high temperature visible-blind UV detection. Published by AIP Publishing

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Transient photovoltage in GaN as measured by atomic force microscope tip

Cited by 40 publications

References 22 publications

Transient photoluminescence of shallow donor bound excitons in GaN

Transient photoluminescence of shallow donor bound excitons in GaN

Transient photovoltage in GaN

High-temperature ultraviolet detection based on surface photovoltage effect in SiN passivated n-GaN films

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