Metastability and persistent photoconductivity in Mg-doped <i>p</i>-type GaN

Johnson, C. M.; Lin, J. Y.; Jiang, H. X.; Khan, M. Asif; Sun, C. J.

doi:10.1063/1.116020

Cited by 155 publications

(84 citation statements)

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“…͑1͒. The stretched-exponential relaxation is commonly observed in disordered systems, 26,28,30,33,37,40,41 which implies that the origin of the observed PPC effect has a similar property. A least-squares fit to the experimental data yields a time constant and decay exponent ␤ values.…”

Section: Resultsmentioning

confidence: 72%

“…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%

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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: 72%

Section: Resultsmentioning

confidence: 99%

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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“…P-type conductivity in GaN is the key for producing the optoelectronics devices. Mg has been widely used [2] [13] despite its intrinsic difficulties. It is nowadays well established that during the growth process of Mg doped GaN, atomic H is generated from the decomposition of NH 3 and Mg-H complexes are formed in the layer [3] [4] [5].…”

Section: Introductionmentioning

confidence: 99%

p-doping of GaN by MOVPE

Haffouz

Beaumont

Leroux

et al. 1997

MRS Internet j. nitride semicond. res.

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Mg has been widely used as p-doping species despite its intrinsic difficulties. It is nowadays well established that during the growth process of Mg doped GaN, atomic H is generated from the decomposition of NH 3 and Mg-H complexes are formed in the layer. This has been for instance shown by the occurrence of LO mode in IR absorption, and by the observation of the Mg-H local vibration modes. This H passivation limits the electrical activity of Mg, therefore an activation process is required to get full activation of the Mg atoms. In the present study, bismethylcyclopentadienyl magnesium [(MeCp) 2 Mg] was used as precursor. However, this precursor reacts in the gas phase with NH 3 to produce tiny solid particles as evidenced by a very bright diffuse emission visible along the laser beam used for reflectometry measurements. This simplest obvious product would be [(MeCp)Mg(NH 2 )] m (m≥2). To limit this drawback, Ga and Mg precursor lines have been separated. With proper in situ heat treatment, doping densities up to 1.5x10 18 cm -3 have been obtained. PL spectra of lightly Mg doped samples (10 16 cm -3 ) are dominated by shallow donor-acceptor pairs whereas for higher doping densities ( 10 18 cm -3 ), the luminescence is dominated by a broad band in the 2.7-2.9 eV range. GaN LEDs were fabricated from Si doped (n-type) and Mg-doped (p-type) GaN, these LEDs emit in the blue-UV range.

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“…Nano-scale clusters of Zn Cu anti-site donors have already been reported in CZTS [45]. However, local potential fluctuations are also reported to be caused by compositional fluctuations in sulphur and selenium-based II-VI semiconductor alloys [16,[34][35][36]. In this case, fluctuations in the conduction and valences band edges will be opposite, leaving them antiparallel to each other.…”

Section: Resultsmentioning

confidence: 95%

Anomalous persistent photoconductivity in Cu2ZnSnS4 thin films and solar cells

Abelenda

Sánchez

Ribeiro

et al. 2015

Solar Energy Materials and Solar Cells

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Persistent photoconductivity effect (PPC) has been investigated in Cu 2 ZnSnS 4 thin films and solar cells as a function of temperature. An anomalous increase of the PPC decay time with temperature was observed in all samples. The PPC decay time activation energy was found to increase when temperature rises above a crossover value, and also to growth with the increase of the sulphurization temperature and pressure. Both, the anomalous behavior of the PPC decay time and the existence of two different activation energies are explained in terms of local potential fluctuations in the band edges of CZTS.

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Metastability and persistent photoconductivity in Mg-doped p-type GaN

Cited by 155 publications

References 0 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

p-doping of GaN by MOVPE

Anomalous persistent photoconductivity in Cu2ZnSnS4 thin films and solar cells

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