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17 Sep 2012

Volume 101, Issue 12, Articles (12xxxx)

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Appl. Phys. Lett. 101, 123901 (2012); http://dx.doi.org/10.1063/1.4751469 (4 pages)

Chin-An Lin, K. P. Huang, S. T. Ho, Mei-Wen Huang, and Jr-Hau He
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Efficient physical-thermal model for thermal effects in AlGaN/GaN high electron mobility transistors

M. Rousseau, A. Soltani, and J. C. De Jaeger

Appl. Phys. Lett. 101, 122101 (2012); http://dx.doi.org/10.1063/1.4753815 (3 pages)

Online Publication Date: 17 September 2012

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This letter describes the thermal behavior of AlGaN/GaN high electron mobility transistors on different substrates thanks to a fully consistent physical-thermal model. Self-heating explains the drastic reduction in the current flowing from drain to source. It is shown that, in order to keep the material from significantly degrading at the gate exit, the maximum dissipated power must be limited to 7 W/mm, 13 W/mm, and 38 W/mm for silicon, silicon carbide, and diamond substrates, respectively. These results have been validated from experimental thermal measurements.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Studies on atomic layer deposition Al2O3/In0.53Ga0.47As interface formation mechanism based on air-gap capacitance-voltage method

Toshiyuki Yoshida and Tamotsu Hashizume

Appl. Phys. Lett. 101, 122102 (2012); http://dx.doi.org/10.1063/1.4753927 (4 pages)

Online Publication Date: 18 September 2012

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The air-gap capacitance-voltage characteristics of InGaAs surfaces were measured after 1-, 2-, 6-, 9-, and 17-cycle atomic layer deposition (ALD) Al2O3 processing. A high density of mid-gap states was found to be generated and increased during these ALD process steps, while the native oxide component was reduced. On the other hand, the mid-gap state density was drastically reduced after the usual annealing process. The generation of the mid-gap states seemed to be relevant to a non-stoichiometric Al-oxide component associated with a deficit in oxygen atoms, which became re-oxidized during the annealing process.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Cc Kinetics of defect formation and annealing
73.20.At Surface states, band structure, electron density of states
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Polarization induced pn-junction without dopant in graded AlGaN coherently strained on GaN

Shibin Li, Morgan Ware, Jiang Wu, Paul Minor, Zhiming Wang, Zhiming Wu, Yadong Jiang, and Gregory J. Salamo

Appl. Phys. Lett. 101, 122103 (2012); http://dx.doi.org/10.1063/1.4753993 (3 pages) | Cited 7 times

Online Publication Date: 18 September 2012

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We propose a type of pn-junction not formed by impurity-doping, but rather by grading the Al composition in an AlxGa1−xN thin film, resulting in alternating p and n conducting regions due to polarization charge. By linearly grading AlxGa1−xN from 0% to x (x ≤ 30%) and back to 0% Al, a polarization induced pn-junction is formed, even in the absence of any impurity doping. X-ray diffraction reciprocal space maps are used to determine the strain state of the different graded composition samples. Polarization induced doping also provides a solution to the problem of p-type doping efficiency for III-nitrides.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ey III-V semiconductors

Donor and acceptor levels in ZnO homoepitaxial thin films grown by molecular beam epitaxy and doped with plasma-activated nitrogen

Pierre Muret, Dimitri Tainoff, Christian Morhain, and Jean-Michel Chauveau

Appl. Phys. Lett. 101, 122104 (2012); http://dx.doi.org/10.1063/1.4751857 (4 pages)

Online Publication Date: 19 September 2012

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Deep level transient spectroscopy of both majority and minority carrier traps is performed in a n-type, nitrogen doped homoepitaxial ZnO layer grown on a m-plane by molecular beam epitaxy. Deep levels, most of them being not detected in undoped ZnO, lie close to the band edges with ionization energies in the range 0.12–0.60 eV. The two hole traps with largest capture cross sections are likely acceptors, 0.19 and 0.48 eV from the valence band edge, able to be ionized below room temperature. These results are compared with theoretical predictions and other experimental data.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
71.55.Gs II-VI semiconductors
73.61.Ga II-VI semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Impact of oxygen annealing on high-k gate stack defects characterized by random telegraph noise

Hsu Feng Chiu, San Lein Wu, Yee Shyi Chang, Shoou Jinn Chang, Jone Fang Chen, Shih Chang Tsai, Che Hua Hsu, Chien Ming Lai, Chia Wei Hsu, and Osbert Cheng

Appl. Phys. Lett. 101, 122105 (2012); http://dx.doi.org/10.1063/1.4753997 (3 pages)

Online Publication Date: 19 September 2012

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The impact of post metal-deposition annealing (PMA) on the trap behavior of high-k/metal-gate metal-oxide-semiconductor field-effect transistors has been studied using drain current random telegraph noise (RTN). The RTN phenomenon is influenced by both trap positions and trap energy, thus corresponding with the PMA passivation mechanism. We found that trap positions in mono-metal-layer annealed (TiN annealed) devices are closer to the TiN/HfO2 interface due to the substitution of nitrogen atoms by oxygen atoms inside the TiN layer. However, replaced nitrogen atoms from TaN can passivate nitrogen defects in TiN that improves device characteristics in dual-metal-layer annealed (TiN/TaN annealed) devices.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Growth study of nonpolar Zn1−xMgxO epitaxial films on a-plane bulk ZnO by plasma-assisted molecular beam epitaxy

Bernhard Laumer, Fabian Schuster, Martin Stutzmann, Andreas Bergmaier, Günther Dollinger, Stephen Vogel, Katharina I. Gries, Kerstin Volz, and Martin Eickhoff

Appl. Phys. Lett. 101, 122106 (2012); http://dx.doi.org/10.1063/1.4754076 (4 pages)

Online Publication Date: 20 September 2012

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Nonpolar Zn1−xMgxO epitaxial films were grown by plasma-assisted molecular beam epitaxy on a-plane ZnO substrates. A smooth surface morphology was accomplished under oxygen-rich growth conditions. The benefits of the use of ZnO substrates on the structural properties are reflected by a low-density of threading dislocations. Furthermore, no indications for the generation of basal plane stacking faults are found. The pseudomorphic growth on a-plane ZnO substrates efficiently locks the epitaxial Zn1−xMgxO films to the wurtzite structure up to x = 0.25. The Mg concentration is not constant and increases with larger thickness. The optical properties reflect the influence of alloy disorder.
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81.05.Dz II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.bg Semiconductors
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Nn Stacking faults and other planar or extended defects
78.66.Hf II-VI semiconductors

Transparent p-type AlN:SnO2 and p-AlN:SnO2/n-SnO2:In2O3 p-n junction fabrication

Y. S. Liu, C. I. Hsieh, Y. J. Wu, Y. S. Wei, P. M. Lee, and C. Y. Liu

Appl. Phys. Lett. 101, 122107 (2012); http://dx.doi.org/10.1063/1.4754134 (4 pages)

Online Publication Date: 20 September 2012

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This study produced transparent p-type AlN-doped SnO2 thin films by annealing sputtered sandwich SnO2/AlN/SnO2 thin films. Both Al3+-Sn4+ and N3−O2− substitution reactions—which are the main sources for the hole carriers—were identified by XPS analysis. The hole concentration of the p-type AlN:SnO2 thin films was as high as 1.074 × 1019 cm−3. Using the produced p-AlN:SnO2 thin film, transparent p-AlN:SnO2/n-SnO2:In2O3 p-n junctions were fabricated and characterized as follows: (1) A low leakage current (2.97 × 10−5 A at −5 V); (2) a 2.17 eV turn-on voltage; and (3) a low ideality factor (12.2).
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
79.60.Dp Adsorbed layers and thin films
81.15.Cd Deposition by sputtering
72.20.Fr Low-field transport and mobility; piezoresistance

W-Sb-Te phase-change material: A candidate for the trade-off between programming speed and data retention

Cheng Peng, Liangcai Wu, Feng Rao, Zhitang Song, Pingxiong Yang, Hongjia Song, Kun Ren, Xilin Zhou, Min Zhu, Bo Liu, and Junhao Chu

Appl. Phys. Lett. 101, 122108 (2012); http://dx.doi.org/10.1063/1.4754138 (5 pages) | Cited 1 time

Online Publication Date: 20 September 2012

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W-Sb-Te phase-change material has been proposed to improve the performance of phase-change memory (PCM). Crystallization temperature, crystalline resistance, and 10-year data retention of Sb2Te increase markedly by W doping. The Wx(Sb2Te)1−x films crystallize quickly into a stable hexagonal phase with W uniformly distributing in the crystal lattice, which ensures faster SET speed and better operation stability for the application in practical device. PCM device based on W0.07(Sb2Te)0.93 shows ultrafast SET operation (6 ns) and good endurance (1.8 × 105 cycles). W-Sb-Te material is a promising candidate for the trade-off between programming speed and data retention.
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84.30.Sk Pulse and digital circuits
64.70.dg Crystallization of specific substances
61.43.-j Disordered solids

Robust low resistivity p-type ZnO:Na films after ultraviolet illumination: The elimination of grain boundaries

S. S. Lin

Appl. Phys. Lett. 101, 122109 (2012); http://dx.doi.org/10.1063/1.4754003 (4 pages) | Cited 1 time

Online Publication Date: 21 September 2012

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We propose negatively charged oxygen species at grain boundaries may be detrimental to the p-type behavior. After ultraviolet illumination to release oxygen species, the p-type behavior of moderately Na-doped ZnO films is strengthened in the subsequent several minutes. A robust p-type film with a hole mobility of 7.9 cm2/Vs, a hole concentration of 2.1 × 1017 cm−3, and a film resistivity of 3.8 Ωcm has been reproducibly achieved. Transformation from n-type to p-type conduction is observed for the lightly Na-doped ZnO after ultraviolet illumination. We believe that single crystalline p-type ZnO films are indispensable for ZnO light-emitting diodes.
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73.61.Ga II-VI semiconductors
61.72.Mm Grain and twin boundaries
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
68.55.-a Thin film structure and morphology
72.20.Fr Low-field transport and mobility; piezoresistance

Valence band offset at Al2O3/In0.17Al0.83N interface formed by atomic layer deposition

M. Akazawa and T. Nakano

Appl. Phys. Lett. 101, 122110 (2012); http://dx.doi.org/10.1063/1.4754141 (4 pages)

Online Publication Date: 21 September 2012

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The valence band offset, ΔEV, at an Al2O3/In0.17Al0.83N interface formed by atomic layer deposition was measured by x-ray photoelectron spectroscopy. The conventional method of using the core level separation, ΔECL, between O 1s and In 4d resulted in ΔEV = 1.3 eV, which was apparently consistent with the direct observation of the valence band edge varying the photoelectron exit angle, θ. However, ΔECL and full width at half maximum of core-level spectra were dependent on θ, which indicated significant potential gradients in Al2O3 and InAlN layers. An actual ΔEV of 1.2 eV was obtained considering the potential gradients.
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71.20.Ps Other inorganic compounds
73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures
81.15.Kk Vapor phase epitaxy; growth from vapor phase
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
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