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20 Feb 2012

Volume 100, Issue 8, Articles (08xxxx)

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Appl. Phys. Lett. 100, 082401 (2012); http://dx.doi.org/10.1063/1.3684972 (4 pages)

Elizabeth Rapoport and Geoffrey S. D. Beach
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Impact of the misfit dislocations on two-dimensional electron gas mobility in semi-polar AlGaN/GaN heterostructures

Guipeng Liu, Ju Wu, Guijuan Zhao, Shuman Liu, Wei Mao, Yue Hao, Changbo Liu, Shaoyan Yang, Xianglin Liu, Qinsheng Zhu, and Zhanguo Wang

Appl. Phys. Lett. 100, 082101 (2012); http://dx.doi.org/10.1063/1.3688047 (4 pages) | Cited 3 times

Online Publication Date: 21 February 2012

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The mobility of two-dimensional electron gas as influenced by the charged misfit dislocations located at the interface of the semi-polar AlGaN/GaN heterostructure is quantitatively analyzed. The results indicate that the strength of the scattering due to the misfit dislocations in the semi-polar AlGaN/GaN heterointerface is comparable to the well-known scattering associated with the threading dislocations in the well-known polar c-plane AlGaN/GaN heterostructures.
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81.05.Ea III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)

Plasmonic detector/spectrometer of subterahertz radiation based on two-dimensional electron system with embedded defect

V. M. Muravev and I. V. Kukushkin

Appl. Phys. Lett. 100, 082102 (2012); http://dx.doi.org/10.1063/1.3688049 (3 pages) | Cited 2 times

Online Publication Date: 21 February 2012

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We demonstrate that the introduction of a defect in the form of an electron density step into a two-dimensional electron system (2DES) locally rectifies the alternating potential of plasma waves. The rectification mechanism is active at temperatures up to room temperature. We observe photovoltage oscillations in a back-gated 2DES with a density defect, when tuning the density under incident subterahertz radiation. The oscillations originate from the interference of 2D plasma waves excited by subterahertz radiation. The period of oscillations depends on the radiation wavelength. These phenomena can be exploited further to produce detectors/spectrometers for millimeter waves.
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85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Assessment of deep level defects in m-plane GaN grown by metalorganic chemical vapor deposition

T. A. Henry, A. Armstrong, K. M. Kelchner, S. Nakamura, S. P. DenBaars, and J. S. Speck

Appl. Phys. Lett. 100, 082103 (2012); http://dx.doi.org/10.1063/1.3687700 (4 pages) | Cited 1 time

Online Publication Date: 22 February 2012

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We report on deep level defect incorporation in n-type m-plane (10math0) GaN grown by metalorganic chemical vapor deposition (MOCVD) on bulk m-plane GaN substrates. Deep levels were observed at 2.85 eV and 3.31 eV relative to the conduction band minimum. While the energetic distribution of defect states for m-plane GaN was similar to the previous reports of n-type c-plane GaN grown by MOCVD, the deep level densities of the m-plane GaN were significantly lower. The comparatively low defect density in homoepitaxially grown m-plane GaN is attributed to reduced point defect incorporation. In addition to the absence of polarization fields, the low deep level density achieved by homoepitaxial growth on high quality bulk GaN substrates makes m-plane GaN highly attractive for opto-electronic devices.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
71.55.Eq III-V semiconductors
81.05.Ea III-V semiconductors

Optical observation of single-carrier charging in type-II quantum ring ensembles

R. J. Young, E. P. Smakman, A. M. Sanchez, P. Hodgson, P. M. Koenraad, and M. Hayne

Appl. Phys. Lett. 100, 082104 (2012); http://dx.doi.org/10.1063/1.3688037 (4 pages) | Cited 4 times

Online Publication Date: 22 February 2012

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A high-purity GaSb/GaAs quantum ring system is introduced that provides both strong hole-confinement in the GaSb ring and electron confinement in its GaAs core. The latter is responsible for a reduced inhomogeous linewidth measured in photoluminescence, in comparison to the previous measurements made on nanostructures with differing morphology in this material system. This allows the resolution of multiple peaks in the photoluminescence due to discrete charging with holes, revealing the mechanism responsible for the excitation-power-induced blueshift.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Cr III-V semiconductors

Characterization of silicon dioxide films on 4H-SiC Si (0001) face by cathodoluminescence spectroscopy and x-ray photoelectron spectroscopy

M. Yoshikawa, S. Ogawa, K. Inoue, H. Seki, Y. Tanahashi, H. Sako, Y. Nanen, M. Kato, and T. Kimoto

Appl. Phys. Lett. 100, 082105 (2012); http://dx.doi.org/10.1063/1.3688173 (4 pages) | Cited 1 time

Online Publication Date: 22 February 2012

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We measured cathodoluminescence (CL) spectra of SiO2 films grown on 4H-SiC wafers and found that for an acceleration voltage of 5 kV, CL peaks at 460 and 490 nm, assigned to oxygen vacancy centers (OVCs), become weak by post-oxidation annealing in N2O ambient at 1300 °C whereas the CL peak around 580 nm, related to Si-N bonding structures, becomes intense. Furthermore, the peak assigned to N-Si3 configurations in x-ray photoelectron spectroscopy (XPS) spectra was observed in the SiO2/SiC interface in only samples annealed in N2O ambient. These results suggest that the interface trap densities decrease and the channel mobility in n-type MOS capacitors increases by the termination of dangling bonds by the N atom in the SiO2/SiC interface. CL spectroscopy and XPS provide us with extensive information on OVCs and dangling bonds in the SiO2/SiC interface on the 4H-SiC substrate.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Nk Insulators
81.40.Gh Other heat and thermomechanical treatments
61.72.jd Vacancies
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Coupling resistance between n-type surface accumulation layer and p-type bulk in InN:Mg thin films

Christophe A. Hurni, Soojeong Choi, Oliver Bierwagen, and James S. Speck

Appl. Phys. Lett. 100, 082106 (2012); http://dx.doi.org/10.1063/1.3680102 (4 pages) | Cited 3 times

Online Publication Date: 22 February 2012

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Indium nitride is the least studied of the III-nitride though it has great potential due to its small bandgap of 0.65 eV and a small effective electron mass. InN:Mg was recently confirmed to be p-type. However, Hall measurements on InN:Mg still show n-type conductivity, even when InN:Mg is very thick. Some studies have suggested the possibility of a high coupling resistance between the surface electron accumulation and the bulk p-InN. In this study, we show through vertical and transmission-line model measurement that this coupling resistance is small and should not affect conductivity and Hall measurements.
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73.61.Ey III-V semiconductors
68.55.ag Semiconductors
71.20.Nr Semiconductor compounds
81.05.Ea III-V semiconductors

Thermoelectric properties and structural variations in Bi2Te3−xSx crystals

W. Wong-Ng, H. Joress, J. Martin, P. Y. Zavalij, Y. Yan, and J. Yang

Appl. Phys. Lett. 100, 082107 (2012); http://dx.doi.org/10.1063/1.3688485 (4 pages) | Cited 2 times

Online Publication Date: 23 February 2012

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We report the application of a custom-designed, non-destructive Seebeck coefficient screening technique, in combination with x-ray diffraction and Hall measurements, to characterize the effect of S substitution on n-type Bi2Te3−xSx single crystals. The results elucidate the detailed distribution of Te/S in the Bi2Te3−xSx crystals, including the preferred substitution site, to correlate the compositional gradient with the transport properties in different locations on the same crystal. As the S substitution increases, the carrier concentration increases, and the absolute Seebeck coefficient decreases. The observed trends in the transport properties and the compositional variations are consistent with a narrow gap semiconductor model.
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72.20.Pa Thermoelectric and thermomagnetic effects
72.20.My Galvanomagnetic and other magnetotransport effects
61.66.Fn Inorganic compounds

Thermal conductivity of 1.3 μm InAs/GaAs quantum dot laser active material from chirp and 3ω measurements

Zhongyang Ge, Patricia Moat, Jing Xie, Junjie Hu, Jia-Sheng Huang, Xinyu Sun, Neinyi Li, B. E. White, Jr., and David Klotzkin

Appl. Phys. Lett. 100, 082108 (2012); http://dx.doi.org/10.1063/1.3687160 (4 pages)

Online Publication Date: 23 February 2012

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Semiconductor quantum dots have very low thermal conductivities compared with bulk materials or quantum well structures. In this paper, thermal conductivity of InAs quantum dot laser active regions was determined using two different approaches. Measured conductivity is between 0.03 and 0.05 W/(m-K) for both approaches, in reasonable agreement considering the approximations used in the measurement method. This reduced thermal conductivity of the active region in quantum dot lasers has a significant effect on the laser operating characteristics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Phonon spectrum and bonding properties of Bi2Se3: Role of strong spin-orbit interaction

Bao-Tian Wang and Ping Zhang

Appl. Phys. Lett. 100, 082109 (2012); http://dx.doi.org/10.1063/1.3689759 (4 pages) | Cited 4 times

Online Publication Date: 23 February 2012

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Phonon dispersions of one typical three-dimensional topological insulator Bi2Se3 have been studied within density functional theory. The soft modes of two acoustic branches along the Z – F and Γ-F directions within the pure local density approximation will transit to show imaginary frequency oscillating after including the spin-orbit interaction (SOI). Similar phenomenon has also been observed for Bi2Te3. Besides, we have found that the weak van der Waals forces between two Se1 layers in Bi2Se3 are strengthened by turning on the spin-orbit interaction.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Ps Other inorganic compounds
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Interface nature of oxidized single-crystal arrays of etched Si nanowires on (100)Si

M. Jivanescu, A. Stesmans, R. Kurstjens, and F. Dross

Appl. Phys. Lett. 100, 082110 (2012); http://dx.doi.org/10.1063/1.3682315 (4 pages) | Cited 2 times

Online Publication Date: 23 February 2012

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Low temperature electron spin resonance studies have been carried out on single crystalline arrays of sub-10 nm Si nanowires (NWs) manufactured on (100)Si by top down etching and oxidation thinning. This reveals the presence of a substantial inherent density of Pb0 (Si3 ≡ Si•) defects (traps) at the NW Si/SiO2 interfaces, due to particular faceting and enhanced interface strain, leaving NW interfaces of reduced electrical quality. Perusal of the specific properties of the occurring Pb-type defect system points to a nanopillar morphology compatible with NWs predominantly bordered by {110} facets, with cross sectional shape of 〈100〉 truncated {110} squares. The inherent interface quality appears limited by the wire-narrowing thermal oxidation procedure.
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81.65.Cf Surface cleaning, etching, patterning
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
76.30.Mi Color centers and other defects
61.72.J- Point defects and defect clusters

Measuring the concentration and energy distribution of interface states using a non-contact corona oxide semiconductor method

J. E. de Vries and Y. Rosenwaks

Appl. Phys. Lett. 100, 082111 (2012); http://dx.doi.org/10.1063/1.3689004 (3 pages) | Cited 1 time

Online Publication Date: 24 February 2012

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The electronic states distribution at the Si-SiO2 interface was measured by combining contactless corona charge-voltage measurement and low-frequency capacitance voltage method. Using device equivalent circuit modeling, we were able to obtain the silicon-insulator interface states energy distribution across the whole Si band gap with a single measurement. The measured distribution has the well known u-shaped curve, with a minimum around mid gap of 2 × 1010 cm−2 eV−1 and maximum values close to the band edges reaching 6 × 1013 cm−2 eV−1. Two distinct peaks were observed at 0.21 eV and 0.88 eV above the valence band maximum which correspond to the Si (100) Pb0 centers.
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73.20.At Surface states, band structure, electron density of states
71.20.Mq Elemental semiconductors

Comparison of thermal and atomic-layer-deposited oxides on 4H-SiC after post-oxidation-annealing in nitric oxide

Changhyun Kim, Jeong Hyun Moon, Jeong Hyuk Yim, Do Hyun Lee, Jong Ho Lee, Hun Hee Lee, and Hyeong Joon Kim

Appl. Phys. Lett. 100, 082112 (2012); http://dx.doi.org/10.1063/1.3689766 (4 pages) | Cited 1 time

Online Publication Date: 24 February 2012

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The electrical properties of thermally grown and atomic-layer-deposition (ALD) oxides, followed by nitridation treatment, on 4H-SiC substrate were compared. The nitridation treatment was performed with post oxidation annealing in NO atmosphere (NO POA). The best electrical characteristics of the thermally grown and ALD oxides were observed at 120 and 180 min NO POA, respectively. The NO POA treated ALD oxide showed extremely low interface trap density (Dit), less than 1011 eV−1 cm−1. A metal-oxide-semiconductor field-effect-transistor with the ALD oxide showed high field effect mobility, especially in the high electric field region. The reasons for these superior results were also discussed.
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81.20.-n Methods of materials synthesis and materials processing
81.40.Gh Other heat and thermomechanical treatments
81.65.Mq Oxidation
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