The role of the grain boundary on persistent photoconductivity in GaN

Sarkar, Niladri; Dhar, Subhabrata; Ghosh, Subhasis

doi:10.1088/0953-8984/15/43/015

Cited by 15 publications

(13 citation statements)

References 64 publications

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“…Such PPC behavior has been observed in many III-V and II-VI semiconductor thin films and heterostructures. [19][20][21][22][23][24][25][26]28,[30][31][32][38][39][40][41] The origin of the PPC can be explained by the fact that the photoexcited carriers are trapped and spatially separated by local potential fluctuations, which then suppresses the recombination of carriers. The Al content affects the PPC decay rate.…”

Section: Resultsmentioning

confidence: 99%

“…The carrier capture process, from weakly localized states to strongly localized states of deeper potential by alloy fluctuations, causes a slow decay in PPC. 19,22 In addition, the stretched-exponential relaxation is commonly observed in disordered samples. 24,31 The persistent increase in the conductivity in the 2DEG channel after the illumination of the PPC in AlGaN/GaN heterostructures can be explained via three possible mechanisms.…”

Section: Resultsmentioning

confidence: 99%

“…16͒ and III-V ͑Refs. 17 and 18͒ semiconductors, including the p-and n-type GaN epilayers, 19 Si or Se doped n-type GaN, 2,20 or Mg doped GaN, 20,21 AlGaN/GaN heterostructures, [22][23][24][25] and AlGaN epilayers. 25,26 Other related studies are rather useful for understanding the metastable properties of defects, the mechanisms for carrier storage and relaxation, and the transport properties in a disordered system.…”

Section: Introductionmentioning

confidence: 99%

“…21,30 In the GaN and Al x Ga 1−x N epilayers, this was similarly ascribed to defect complexes such as gallium vacancies, nitrogen antisites, deep-level impurities, and interacting defect complexes. 19,20,28,29,[31][32][33][34] In the literature, several studies can be found about PPC experiments on Al x Ga 1−x N / GaN heterostructures. [22][23][24][25] In those studies, the persistent increase in the carrier concentration was explained by the transfer of photoexcited electrons from the deep-level impurities in the Al x Ga 1−x N layers.…”

Section: Introductionmentioning

confidence: 99%

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The persistent photoconductivity effect in AlGaN/GaN heterostructures grown on sapphire and SiC substrates

Arslan

Bütün

Li̇şesi̇vdi̇n

et al. 2008

Journal of Applied Physics

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In the present study, we reported the results of the investigation of electrical and optical measurements in Al x Ga 1−x N / GaN heterostructures ͑x = 0.20͒ that were grown by way of metal-organic chemical vapor deposition on sapphire and SiC substrates with the same buffer structures and similar conditions. We investigated the substrate material effects on the electrical and optical properties of Al 0.20 Ga 0.80 N / GaN heterostructures. The related electrical and optical properties of Al x Ga 1−x N / GaN heterostructures were investigated by variable-temperature Hall effect measurements, photoluminescence ͑PL͒, photocurrent, and persistent photoconductivity ͑PPC͒ that in turn illuminated the samples with a blue ͑ = 470 nm͒ light-emitting diode ͑LED͒ and thereby induced a persistent increase in the carrier density and two-dimensional electron gas ͑2DEG͒ electron mobility. In sample A ͑Al 0.20 Ga 0.80 N / GaN/ sapphire͒, the carrier density increased from 7.59ϫ 10 12 to 9.9ϫ 10 12 cm −2 via illumination at 30 K. On the other hand, in sample B ͑Al 0.20 Ga 0.80 N / GaN/ SiC͒, the increments in the carrier density were larger than those in sample A, in which it increased from 7.62ϫ 10 12 to 1.23ϫ 10 13 cm −2 at the same temperature. The 2DEG mobility increased from 1.22ϫ 10 4 to 1.37ϫ 10 4 cm −2 / V s for samples A and B, in which 2DEG mobility increments occurred from 3.83ϫ 10 3 to 5.47ϫ 10 3 cm −2 / V s at 30 K. The PL results show that the samples possessed a strong near-band-edge exciton luminescence line at around 3.44 and 3.43 eV for samples A and B, respectively. The samples showed a broad yellow band spreading from 1.80 to 2.60 eV with a peak maximum at 2.25 eV with a ratio of a near-band-edge excitation peak intensity up to a deep-level emission peak intensity ratio that were equal to 3 and 1.8 for samples A and B, respectively. Both of the samples that were illuminated with three different energy photon PPC decay behaviors can be well described by a stretched-exponential function and relaxation time constant as well as a decay exponent ␤ that changes with the substrate type. The energy barrier for the capture of electrons in the 2DEG channel via the deep-level impurities ͑DX-like centers͒ in AlGaN for the Al 0.20 Ga 0.80 N / GaN/sapphire and Al 0.20 Ga 0.80 N / GaN/ SiC heterojunction samples are 343 and 228 meV, respectively. The activation energy for the thermal capture of an electron by the defects ⌬E changed with the substrate materials. Our results show that the substrate material strongly affects the electrical and optical properties of Al 0.20 Ga 0.80 N/GaN heterostructures. These results can be explained with the differing degrees of the lattice mismatch between the grown layers and substrates.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The persistent photoconductivity effect in AlGaN/GaN heterostructures grown on sapphire and SiC substrates

Arslan

Bütün

Li̇şesi̇vdi̇n

et al. 2008

Journal of Applied Physics

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“…Considering the wide direct bandgap, nanometer-scale dimensions, and also taking advantage of the high aspect ratio and rough surfaces, electrospun GaN nanofibers are suitable for ultraviolet photodetection applications. [23][24][25] Figure 3 is the photoconductance response of the GaN nanofiber FET device. The current was monitored at a bias of V g ¼ 0 and V sd ¼ 1 V while 254 nm wavelength UV light with a power density of 3 mW cm À2 was turned on and off repeatedly for five cycles.…”

mentioning

confidence: 99%

GaN Nanofibers based on Electrospinning: Facile Synthesis, Controlled Assembly, Precise Doping, and Application as High Performance UV Photodetector

et al. 2009

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Nitride nanofibers have been synthesized based on a simple electrospinning technique for the first time. No catalysts or templates are needed in this new synthetic method. Highly oriented GaN nanofiber arrays, as well as a high‐performance UV photodetector based on single GaN nanofiber assembled FET devices, can be facilely fabricated using this technique. Precise doping of other elements into the GaN nanofibers is easy by this solution‐based synthetic method.

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Time‐resolved free carrier lifetime microscopy in bulk GaN

Šcˇajev

Наргелас

Jarašiūnas

2013

Physica Rapid Research Ltrs

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A novel setup for lifetime microscopy measurements was designed and applied for carrier lifetime mapping in a bulk GaN. Photoexcitation by a picosecond UV pump and detection of time‐resolved free carrier absorption (FCA) images on a CCD camera enabled the mapping of carrier lifetime distribution with a spatial resolution of 5 μm. The spatial variation of lifetime in the bulk HVPE‐grown GaN revealed the presence of different‐size crystalline grains, with lifetime peaking up to 70 ns in the centers of the largest grains (∼20 μm in diameter) and dropping to 10 ns in the small ones, while the spatially averaged lifetime was 40 ns. The inhomogeneity was ascribed to the interplay of nonradiative diffusion‐limited recombination at grain boundaries and a bulk lifetime in the crystallite centers. The numerical solution of spatially‐resolved carrier decay rate in the crystallite centers at high injection levels and comparison with experimental data provided a bulk nonradiative recombination time of ∼70 ns. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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The role of the grain boundary on persistent photoconductivity in GaN

Cited by 15 publications

References 64 publications

The persistent photoconductivity effect in AlGaN/GaN heterostructures grown on sapphire and SiC substrates

The persistent photoconductivity effect in AlGaN/GaN heterostructures grown on sapphire and SiC substrates

GaN Nanofibers based on Electrospinning: Facile Synthesis, Controlled Assembly, Precise Doping, and Application as High Performance UV Photodetector

Time‐resolved free carrier lifetime microscopy in bulk GaN

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