Two-dimensional electron mobility limitation mechanisms in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>Al</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi>Ga</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:mi mathvariant="normal">N</mml:mi><mml:mo>∕</mml:mo><mml:mi>GaN</mml:mi></mml:mrow></mml:math>heterostructures

Gurusinghe, Manjula; Davidsson, S. K.; Andersson, T. G.

doi:10.1103/physrevb.72.045316

Cited by 189 publications

(99 citation statements)

References 27 publications

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“…[7][8][9]29,35,36 The increments in mobility due to photoexcitation at a fixed temperature can be attributed to the increased electron mean energy with an increasing carrier density in the 2DEG channel, which leads to an improved screening and thereby reduced scattering between the 2DEG electrons with the ionized donor impurities. 24,29 The 9 These results show that there are considerable compressive strains that exist in our GaN layers due to the mismatch between the epilayers.…”

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: 99%

“…35,36 After the deposition of these layers, a 20 nm thick undoped Al 0.20 Ga 0.80 N layer was grown on an AlN barrier layer at 1050°C and, finally, a 3 nm GaN cap layer was grown at the same temperature. At the beginning of the growth, the substrate was baked in H 2 ambient conditions at 1100°C for 5 min in order to remove the native oxide.…”

Section: Methodsmentioning

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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“…The AlN barrier layer was used to reduce the alloy disorder scattering by minimizing the wave function penetration from the 2DEG channel into the Al x Ga 1−x N layer. 15 After the deposition of these layers, a 23 nm thick undoped Al 0.22 Ga 0.78 N layer was grown on an AlN layer at 1050°C. Finally, a 5 nm thick GaN cap layer growth was carried out at a temperature of 1085°C and a pressure of 50 mbars.…”

Section: Methodsmentioning

confidence: 99%

Dislocation-governed current-transport mechanism in (Ni/Au)–AlGaN/AlN/GaN heterostructures

Arslan

Altındal

Özçelik

et al. 2009

Journal of Applied Physics

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The current-transport mechanisms in ͑Ni/ Au͒ -Al 0,22 Ga 0,78 N / AlN/ GaN heterostructures were studied by using temperature dependent forward-bias current-voltage ͑I-V͒ characteristics in the temperature range of 80-410 K. In order to determine the current mechanisms for ͑Ni/ Au͒ -Al 0,22 Ga 0,78 N / AlN/ GaN heterostructures, we fitted the experimental I-V data to the analytical expressions given for the current-transport mechanisms in a wide range of applied biases and at different temperatures. The contributions of thermionic-emission, generation-recombination, tunneling, leakage currents that are caused by inhomogeneities, and defects at the metal-semiconductor interface current mechanisms were all taken into account. The best fitting results were obtained for the tunneling current mechanism. On the other hand, we did not observe sufficient agreement between the experimental data and the other current mechanisms. The temperature dependencies of the tunneling saturation current ͑I t ͒ and tunneling parameters ͑E 0 ͒ were obtained from fitting results. We observed a weak temperature dependence of the saturation current and the absence of the temperature dependence of the tunneling parameters in this temperature range. The results indicate that in the temperature range of 80-410 K, the mechanism of charge transport in the ͑Ni/ Au͒ −Al 0.22 Ga 0.78 N / AlN/ GaN heterostructure is performed by tunneling among those dislocations intersecting the space charge region. The dislocation density ͑D͒ that was calculated from the I-V characteristics, according to a model of tunneling along the dislocation line, gives the value of 0.24ϫ 10 7 cm −2 . This value is close in magnitude to the dislocation density that was obtained from the x-ray diffraction measurements.

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“…While the mobility of sample series 1 is limited by increasing roughness correlated to the higher In content, the dominant scattering mechanisms for sample series 2 are different: the width and position of the 2DEG changes with varying 2DEG densities, which results in different dominant scattering mechanisms. 20 For densities above 7 9 10 12 cm À2 , the distance of the 2DEG from the interface becomes small, therefore interface scattering becomes the dominant mechanism here. For the samples of series 2, all of which have similar interface roughness, we observe exactly the aforementioned behavior.…”

Section: Resultsmentioning

confidence: 99%

Polarization-Engineered Enhancement-Mode High-Electron-Mobility Transistors Using Quaternary AlInGaN Barrier Layers

Reuters

Wille

Ketteniss

et al. 2013

Journal of Elec Materi

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Group III nitride heterostructures with low polarization difference recently moved into the focus of research for realization of enhancement-mode (e-mode) transistors. Quaternary AlInGaN layers as barriers in GaN-based high-electron-mobility transistors (HEMTs) offer the possibility to perform polarization engineering, which allows control of the threshold voltage over a wide range from negative to positive values by changing the composition and strain state of the barrier. Tensile-strained AlInGaN layers with high Al contents generate high two-dimensional electron gas (2DEG) densities, due to the large spontaneous polarization and the contributing piezoelectric polarization. To lower the 2DEG density for e-mode HEMT operation, the polarization difference between the barrier and the GaN buffer has to be reduced. Here, two different concepts are discussed. The first is to generate compressive strain with layers having high In contents in order to induce a positive piezoelectric polarization compensating the large negative spontaneous polarization. Another novel approach is a lattice-matched Ga-rich AlInGaN/GaN heterostructure with low spontaneous polarization and improved crystal quality as strain-related effects are eliminated. Both concepts for e-mode HEMTs are presented and compared in terms of electrical performance and structural properties.

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Two-dimensional electron mobility limitation mechanisms inAlxGa1−xN∕GaNheterostructures

Cited by 189 publications

References 27 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

Dislocation-governed current-transport mechanism in (Ni/Au)–AlGaN/AlN/GaN heterostructures

Polarization-Engineered Enhancement-Mode High-Electron-Mobility Transistors Using Quaternary AlInGaN Barrier Layers

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