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2 Feb 2009

Volume 94, Issue 5, Articles (05xxxx)

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Appl. Phys. Lett. 94, 059901 (2009); http://dx.doi.org/10.1063/1.3086725 (3 pages)

Yuta Tsukada, Tsuyoshi Honma, and Takayuki Komatsu
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Determination of MgO/AlN heterojunction band offsets by x-ray photoelectron spectroscopy

A. L. Yang, H. P. Song, X. L. Liu, H. Y. Wei, Y. Guo, G. L. Zheng, C. M. Jiao, S. Y. Yang, Q. S. Zhu, and Z. G. Wang

Appl. Phys. Lett. 94, 052101 (2009); http://dx.doi.org/10.1063/1.3075060 (3 pages) | Cited 11 times

Online Publication Date: 2 February 2009

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MgO is a promising gate dielectric and surface passivation film for GaN/AlGaN transistors, but little is known of the band offsets in the MgO/AlN system. X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band (ΔEv) of MgO/AlN heterostructures. A value of ΔEv = 0.22±0.08 eV was obtained. Given the experimental band gap of 7.83 eV for MgO, a type-I heterojunction with a conduction band offset of ∼ 1.45 eV is found. The accurate determination of the valence and conduction band offsets is important for use of III-N alloys based electronic devices.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.60.Jv Interfaces; heterostructures; nanostructures
71.20.Nr Semiconductor compounds
81.65.Rv Passivation
85.30.Tv Field effect devices

Compensation and carrier trapping in indium-doped CdTe: Contributions from an important near-mid-gap donor

V. Babentsov, J. Franc, and R. B. James

Appl. Phys. Lett. 94, 052102 (2009); http://dx.doi.org/10.1063/1.3073738 (3 pages) | Cited 7 times

Online Publication Date: 3 February 2009

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We report on the recharging of the neutral state of a deep-donor layer that increases the efficiency of charge collection in detector-grade CdTe:In. Measurements with photoinduced current transient spectroscopy and thermoelectric effect spectroscopy revealed positively charged energy level at EC−0.65 eV. Photoluminescence measurements identified this level being responsible for the 0.68 eV emission band. Its positive charge is converted into a neutral one by the upward displacement of Fermi level. We discuss the nature of this deep defect based on the latest ab initio calculations.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.72.uj III-V and II-VI semiconductors
72.80.Ey III-V and II-VI semiconductors
78.55.Et II-VI semiconductors
71.20.Nr Semiconductor compounds
72.20.Pa Thermoelectric and thermomagnetic effects

Landau level spectrum in a two-dimensional hole gas in C-doped (100) GaAs/Al0.4Ga0.6As square quantum well

Z. Q. Yuan, R. R. Du, M. J. Manfra, L. N. Pfeiffer, and K. W. West

Appl. Phys. Lett. 94, 052103 (2009); http://dx.doi.org/10.1063/1.3077147 (3 pages) | Cited 3 times

Online Publication Date: 3 February 2009

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We study the Landau level spectrum of a two-dimensional hole gas in carbon δ-doped (100) GaAs/Al0.4Ga0.6As square quantum well (width of 15 nm) by means of microwave cyclotron resonance (CR) and tilted field magnetotransport. Only one type of hole, with an effective mass of 0.4me, was detected in CR. By analyzing the spin-splitting level coincident conditions at B ∼ 1 T, we find that the effective g-factor is large enough to cause Landau level crossing even in zero tilt, and the product of gm∗ increases with total magnetic field.
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73.21.Fg Quantum wells
71.70.Di Landau levels
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
72.20.My Galvanomagnetic and other magnetotransport effects
73.63.Hs Quantum wells

Metallic conductivity and the role of copper in ZnO/Cu/ZnO thin films for flexible electronics

K. Sivaramakrishnan and T. L. Alford

Appl. Phys. Lett. 94, 052104 (2009); http://dx.doi.org/10.1063/1.3077184 (3 pages) | Cited 22 times

Online Publication Date: 3 February 2009

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ZnO/Cu/ZnO multilayer structures are obtained with the highest conductivity of dielectric-metal-dielectric films reported in literature with a carrier concentration of 1.2×1022 cm−3 and resistivity of 6.9×10−5 Ω-cm at the optimum copper layer thickness. The peak transmittance, photopic averaged transmittance, and Haacke figure of merit are 88%, 75%, and 8.7×10−3 Ω−1, respectively. The conduction mechanism involves metal to oxide carrier injection prior to the formation of a continuous metal conduction pathway. Optical transmission is elucidated in terms of copper’s absorption due to d-band to Fermi surface transitions at short wavelengths and reflectance combined with scattering losses at long wavelengths.
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73.40.Vz Semiconductor-metal-semiconductor structures
73.20.At Surface states, band structure, electron density of states

Electronic transport and colossal electroresistance in SrTiO3:Nb-based Schottky junctions

D. S. Shang, J. R. Sun, L. Shi, J. Wang, Z. H. Wang, and B. G. Shen

Appl. Phys. Lett. 94, 052105 (2009); http://dx.doi.org/10.1063/1.3077615 (3 pages) | Cited 15 times

Online Publication Date: 3 February 2009

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Current-voltage characteristics and colossal electroresistance (CER) have been experimentally investigated in the temperature range from 293 to 454 K for the Schottky junctions Au/SrTiO3:0.5 wt % Nb and Au/SrTiO3:0.05 wt % Nb. Both junctions show electron tunneling-dominated transport behavior. Postannealing of SrTiO3:0.05 wt % Nb in oxygen atmosphere causes a transition of the transport behavior from electron tunneling to thermionic emission. The CER effect appears in the junctions with the transport behavior dominated by electron tunneling and greatly weakens when thermionic emission prevails after postannealing. This result reveals the presence of a close relation between CER and electron tunneling.
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73.40.Ns Metal-nonmetal contacts
75.47.Gk Colossal magnetoresistance
73.40.Gk Tunneling
79.40.+z Thermionic emission
73.30.+y Surface double layers, Schottky barriers, and work functions
81.40.Gh Other heat and thermomechanical treatments

Energy-band parameters of atomic layer deposited Al2O3 and HfO2 on InxGa1−xAs

M. L. Huang, Y. C. Chang, Y. H. Chang, T. D. Lin, J. Kwo, and M. Hong

Appl. Phys. Lett. 94, 052106 (2009); http://dx.doi.org/10.1063/1.3078399 (3 pages) | Cited 13 times

Online Publication Date: 3 February 2009

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X-ray photoelectron spectroscopy (XPS) combined with reflection electron energy loss spectroscopy (REELS) were used to determine the energy-band parameters, valence-band offsets ΔEV, conduction-band offsets ΔEC, and energy-band gaps Eg, of the atomic layer deposited (ALD) Al2O3 and HfO2 on InxGa1−xAs (x = 0, 0.15, 0.25, and 0.53). Using REELS, Eg values of the ALD-Al2O3 and –HfO2 were estimated to be 6.77 and 5.56±0.05 eV, respectively. The ΔEV’s were determined by measuring the core level to valence band maximum binding energy difference from the XPS spectra. The ΔEC’s were then extracted from ΔEV’s and the energy-band gaps of the oxides and InxGa1−xAs, and are in good agreement with those estimated from the Fowler–Nordheim tunneling. The ΔEC’s and ΔEV’s are larger than 1.5 and 2.5 eV, respectively, for all the ALD-oxide/InxGa1−xAs samples.
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71.20.Ps Other inorganic compounds
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling
79.60.Bm Clean metal, semiconductor, and insulator surfaces
77.55.-g Dielectric thin films
79.20.Uv Electron energy loss spectroscopy
71.20.Nr Semiconductor compounds

Multiple conduction paths in boron δ-doped diamond structures

Niall Tumilty, Joseph Welch, Haitao Ye, Richard S. Balmer, Christopher Wort, Richard Lang, and Richard B. Jackman

Appl. Phys. Lett. 94, 052107 (2009); http://dx.doi.org/10.1063/1.3075860 (3 pages) | Cited 4 times

Online Publication Date: 4 February 2009

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Impedance spectroscopy has been used to investigate conductivity within boron-doped diamond in an intrinsic/delta-doped/intrinsic (i-δ-i) multilayer structure. For a 5 nm thick delta layer, three conduction pathways are observed, which can be assigned to transport within the delta layer and to two differing conduction paths in the i-layers adjoining the delta layer. For transport in the i-layers, thermal trapping/detrapping processes can be observed, and only at the highest temperature investigated (673 K) can transport due to a single conduction process be seen. Impedance spectroscopy is an ideal nondestructive tool for investigating the electrical characteristics of complex diamond structures.
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73.63.-b Electronic transport in nanoscale materials and structures

Anisotropic transport in quantum waveguides due to the spin-orbit interactions

Miao Wang, Kai Chang, and K. S. Chan

Appl. Phys. Lett. 94, 052108 (2009); http://dx.doi.org/10.1063/1.3079400 (3 pages) | Cited 5 times

Online Publication Date: 6 February 2009

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We theoretically investigate the charge transport in the quantum waveguides in the presence of the Rashba spin-orbit interaction and the Dresselhaus spin-orbit interaction. We find that the interplay between the Rashba spin-orbit interaction and Dresselhaus spin-orbit interaction can induce a symmetry breaking and consequently leads to the anisotropic charge transport in the quantum waveguides, the conductance through the quantum waveguides depends sensitively on the crystallographic orientations of the quantum waveguides. The anisotropy of the charge transport can even survive in the presence of disorder effect in realistic systems.
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71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.23.-b Electronic transport in mesoscopic systems
73.63.-b Electronic transport in nanoscale materials and structures

Evaluation of GaN substrates grown in supercritical basic ammonia

Makoto Saito, Hisashi Yamada, Kenji Iso, Hitoshi Sato, Hirohiko Hirasawa, Derrick S. Kamber, Tadao Hashimoto, Steven P. DenBaars, James S. Speck, and Shuji Nakamura

Appl. Phys. Lett. 94, 052109 (2009); http://dx.doi.org/10.1063/1.3079813 (3 pages) | Cited 1 time

Online Publication Date: 6 February 2009

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GaN crystals grown by the basic ammonothermal method were investigated for their use as substrates for device regrowth. X-ray diffraction analysis indicated that the substrates contained multiple grains while secondary ion mass spectroscopy (SIMS) revealed a high concentration of hydrogen, oxygen, and sodium. Despite these drawbacks, the emission from the light emitting diode structures grown by metal organic chemical vapor deposition on both the c-plane and m-plane epitaxial wafers was demonstrated. The SIMS depth profiles showed that the diffusion of the alkali metal from the substrate into the epitaxial film was small, especially in the m-direction.
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68.55.ag Semiconductors
68.55.Nq Composition and phase identification
81.05.Ea III-V semiconductors
81.10.Dn Growth from solutions
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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