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4. GaN-Based Devices for Reliable Operation at Very High Temperatures

Author

Dabiran, Amir M., primary, Osinsky, Andrei V., additional, Peter, Peter P., additional, Fitch, Robert C., additional, Moser, Neil, additional, Crespo, A, additional, Anderson, T J., additional, Ren, F., additional, Khanna, Rohit, additional, Stafford, L., additional, and Pearton, Steve J., additional

Published
2019
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8. Electrical and structural properties of AlN/GaN and AlGaN/GaN heterojunctions.

Author

Polyakov, A. Y., Smirnov, N. B., Govorkov, A. V., Markov, A. V., Yugova, T. G., Dabiran, A. M., Wowchak, A. M., Cui, B., Osinsky, A. V., Chow, P. P., Pearton, S. J., Scherbatchev, K. D., and Bublik, V. T.

Subjects
MOLECULAR beam epitaxy, HETEROSTRUCTURES, SUPERLATTICES, MOLECULAR dynamics, SEMICONDUCTORS
Abstract

The electrical and structural properties of AlN/GaN heterostructures grown by molecular beam epitaxy on sapphire are compared with those of AlGaN/GaN heterostructures. The structural characteristics as assessed by x-ray diffraction show little difference but the electron density in the two-dimensional electron gas is about twice higher for AlN/GaN structures with only slightly lower mobility than in AlGaN/GaN. By proper choice of the Fe doping in GaN(Fe) and the thickness of unintentionally doped GaN layers, the composite buffer of the structure can be made semi-insulating. The current through the AlN/GaN structures is determined by tunneling through the AlN barrier and is much higher than that for AlGaN/GaN films due to the lower thickness of AlN compared to AlGaN. Increasing the thickness of AlN from 3 to 4 nm decreases the leakage current by about an order of magnitude. [ABSTRACT FROM AUTHOR]

Published
2008
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9. Fermi level pinning in heavily neutron-irradiated GaN.

Author

Polyakov, A. Y., Smirnov, N. B., Govorkov, A. V., Markov, A. V., Kolin, N. G., Merkurisov, D. I., Boiko, V. M., Shcherbatchev, K. D., Bublik, V. T., Voronova, M. I., Lee, I-H., Lee, C. R., Pearton, S. J., Dabirian, A., and Osinsky, A. V.

Subjects
GALLIUM nitride, METAL organic chemical vapor deposition, EPITAXY, NEUTRON irradiation, DOPED semiconductors
Abstract

Undoped n-GaN grown by two different metallorganic chemical vapor deposition (MOCVD) techniques, standard MOCVD and epitaxial lateral overgrowth, and Mg-doped p-GaN prepared by hydride vapor phase epitaxy and molecular beam epitaxy were irradiated with fast reactor neutrons to the high fluence of 1018 cm-2. In such heavily irradiated samples the Fermi level is shown to be pinned in a narrow interval of Ec-(0.8-0.95) eV, irrespective of the starting sample properties. The Fermi level pinning position correlates with the measured Schottky barrier height in n-type GaN. The results are interpreted from the standpoint of the existence of the charge neutrality level in heavily disordered material. Based on published theoretical calculations and on deep level transient spectroscopy (measurements and lattice parameter measurements in irradiated material), it is proposed that the Fermi level could be pinned between the gallium-interstitial-related deep donors near Ec-0.8 eV and nitrogen-interstitial-related acceptors near Ec-0.9 eV [ABSTRACT FROM AUTHOR]

Published
2006
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10. Deep hole traps in n-GaN films grown by hydride vapor phase epitaxy.

Author

Polyakov, A. Y., Smirnov, N. B., Govorkov, A. V., Fang, Z.-Q., Look, D. C., Molnar, R. J., and Osinsky, A. V.

Subjects
METALLIC films, EPITAXY
Abstract

Concentrations of deep hole traps were measured in a set of hydride vapor phase epitaxy grown samples with thicknesses varying from 2.6 to 68 µm. Results were obtained from low temperature capacitance-voltage measurements before and after illumination and from deep level transient spectroscopy measurements with optical injection (ODLTS). The former revealed the presence of high densities (∼l0[sup 15] to 10[sup 16] cm[sup -3]) of hole traps whose concentration decreased with sample thickness in a manner similar to that found for the dislocation density. Capacitance versus temperature measurements in the dark and after illumination suggested that these traps form a band of states rather than a single level in the GaN band gap. It is suggested that such states could be associated with dislocations. The main hole traps observed by ODLTS were deep hole traps, of energy near E[sub υ] × 0.9 eV. Their density was also observed to substantially decrease with sample thickness. [ABSTRACT FROM AUTHOR]

Published
2002
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11. Enhanced tunneling in GaN/InGaN multi-quantum-well heterojunction diodes after short-term injection annealing.

Author

Polyakov, A. Y., Smirnov, N. B., Govorkov, A. V., Kim, J., Luo, B., Mehandru, R., Ren, F., Lee, K. P., Pearton, S. J., Osinsky, A. V., and Norris, P. E.

Subjects
QUANTUM wells, DIODES, QUANTUM tunneling
Abstract

Multi-quantum-well GaN/InGaN heterojunction diodes prepared by metalorganic chemical vapor deposition on sapphire showed effects of strong tunneling in their I–V characteristics. The space charge region was shown to be located in the GaN/InGaN superlattice (SL). The injection of moderately high forward currents through the structure for several hours enhanced the overall tunneling through the structure and facilitated faster tunneling between the layers in the GaN/InGaN SL. These results may have relevance to the aging characteristics of light-emitting diodes under bias. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2002
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12. Electronic states in modulation doped p-AlGaN/GaN superlattices.

Author

Polyakov, A. Y., Smirnov, N. B., Govorkov, A. V., Osinsky, A. V., Norris, P. E., Pearton, S. J., Van Hove, J., Wowchack, A. M., and Chow, P. P.

Subjects
DOPED semiconductor superlattices, MOLECULAR beam epitaxy
Abstract

The properties of p-AlGaN/GaN modulation doped superlattices (SLs) prepared by molecular beam epitaxy were studied by means of conductivity versus temperature, admittance spectroscopy, photoinduced current spectroscopy, microcathodoluminescence (MCL) spectra measurements, and measurements of effective diffusion lengths. It is shown that in SLs grown on GaN underlayers the sheet resistivity is about two orders of magnitude lower than for reference p-GaN films and the resistivity of SLs remains lower up to temperatures of about 350 °C. For SLs grown on AlGaN underlayers the gain in resistivity is much more moderate and certain advantages in using such SLs are envisaged only for temperatures below room temperature. The reason for this lower gain is a considerable decrease in hole mobility compared to p-GaN. The effect is somewhat tentatively attributed to worse crystalline perfection of these SLs. It is also shown that such SLs are characterized by a strongly broadened MCL peak and the presence of additional hole traps with activation energy of about 0.4 eV. Despite that, the photosensitivity and MCL intensity of these SLs are much better than for reference p-GaN samples. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2001
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15. Some technology aspects for quantum enestor through AIIIBV multicomponent nanoepitaxy.

Author

Osinsky, V. I., Masol, I. V., Lyahova, N. N., Suhoviy, N. O., Onachenko, M. C., and Osinsky, A. V.

Subjects
NITRIDES, QUANTUM dots, PHOTON detectors, BAND gaps, NANOSTRUCTURED materials, LIGHT
Abstract

For the first time, it has been considered some quantum enestor technology aspects concerning the integration approach for Si-CMOS and site-controlled InGaN/GaN quantum dots, which provides the possibility to realize single photon sources (SPS)/single photon detector (SPD) for quantum processing based on AIIIBV direct bandgap multicomponent heterogeneous nanostructures and their light energy storing capability, by an analogy with the photosynthetic process in plants. [ABSTRACT FROM AUTHOR]

Published
2017
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18. Electron irradiation of AlGaN∕GaN and AlN∕GaN heterojunctions

Author

Polyakov, A. Y., primary, Smirnov, N. B., additional, Govorkov, A. V., additional, Markov, A. V., additional, Pearton, S. J., additional, Dabiran, A. M., additional, Wowchak, A. M., additional, Cui, B., additional, Osinsky, A. V., additional, Chow, P. P., additional, Kolin, N. G., additional, Boiko, V. M., additional, and Merkurisov, D. I., additional

Published
2008
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22. Semi-Insulating, Fe-Doped Buffer Layers Grown by Molecular Beam Epitaxy

Author

Polyakov, A. Y., primary, Smirnov, N. B., additional, Govorkov, A. V., additional, Markov, A. V., additional, Yugova, T. G., additional, Petrova, E. A., additional, Dabiran, A. M., additional, Wowchak, A. M., additional, Osinsky, A. V., additional, Chow, P. P., additional, Pearton, S. J., additional, Shcherbatchev, K. D., additional, and Bublik, V. T., additional

Published
2007
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26. Neutron irradiation effects in p-GaN

Author

Polyakov, A. Y., primary, Smirnov, N. B., additional, Govorkov, A. V., additional, Markov, A. V., additional, Kolin, N. G., additional, Merkurisov, D. I., additional, Boiko, V. M., additional, Shcherbatchev, K. D., additional, Bublik, V. T., additional, Voronova, M. I., additional, Pearton, S. J., additional, Dabiran, A., additional, and Osinsky, A. V., additional

Published
2006
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29. Characterization of High Dose Mn, Fe, and Ni implantation intop-GaN

Author

Pearton, S. J., primary, Overberg, M. E., additional, Thaler, G., additional, Abernathy, C. R., additional, Theodoropoulou, N., additional, Hebard, A. F., additional, Chu, S. N. G., additional, Wilson, R. G., additional, Zavada, J. M., additional, Polyakov, A. Y., additional, Osinsky, A. V., additional, Norris, P. E., additional, Chow, P. P., additional, Wowchack, A. M., additional, Van Hove, J. M., additional, and Park, Y. D., additional

Published
2002
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33. GaN-Based Devices for Reliable Operation at Very High Temperatures

Author

Dabiran, Amir M., Osinsky, Andrei V., Peter, Peter P., Fitch, Robert C., Moser, Neil, Crespo, A, Anderson, T J., Khanna, Rohit, and, Stafford, and Pearton, Steve J.

Abstract

One of the main issues for high-temperature operation of GaN- based devices is the development of reliable metal contacts. We have investigated the thermal stability and device performance of AlGaN/GaN high-electron mobility transistors (HEMTs) with both conventional (Ti/Al/Ni/Au) and Ir-based (Ti/Al/Ir/Au) Ohmic contacts. Both dc and rf measurements showed better performance with Ir-based contacts, from room temperature up to 500{degree sign}C. We also fabricated AlGaN/GaN HEMTs with Ti/Al/TiB2/Ti/Au source/drain Ohmic contacts and a variety of gate metal schemes (Pt/Au, Ni/Au, Pt/TiB2/Au or Ni/TiB2/Au) and subjected them to long-term annealing at 350{degree sign}C. By comparison with companion devices with conventional Ti/Al/Pt/Au Ohmic contacts and Pt/Au gate contacts, the HEMTs with boride- based Ohmic metal and either Pt/Au, Ni/Au or Ni/TiB2/Au gate metal showed superior stability of both source-drain current and transconductance after 25 days aging at 350{degree sign}C.

Published
2006

34. Properties of CdZnO/ZnO Heterostructures for UV Light Emitters

Author

Osinsky, Andrei V., Dong, Jianwei, Hertog, Brian, Dabiran, Amir M., Chow, Peter, Schoenfeld, Winston, Pearton, Steve J., Look, David, and Cartwright, Alexander

Abstract

In the paper we present band-gap alignment diagrams for type-II/type-I heterostructures incorporating the strong piezoelectric and spontaneous polarization fields in ZnCdMgO and AlGaN-based materials and interfaces. The paper describes some of the recent progress made in the development of high quality ZnCdO layers and CdZnO/ZnO heterostructures grown epitaxially by RF-plasma molecular beam epitaxy (MBE). We summarize optical and electrical properties of high quality CdxZn1-xO alloys with Cd mole fraction from 0.02 to 0.78 and discuss phase separation phenomenon, which may be present in ternary alloys. A single-crystal wurtzite structure of CdZnO alloys has been confirmed. We achieved a strong optical emission at RT in the 380 nm to 574 nm spectral range from CdxZn1-xO with various compositions. Dependence of the fundamental optical band gap on the composition of CdxZn1- xO alloys, band gap bowing, and the possible effect of composition micro-fluctuations in ternary CdxZn1-xO alloys on the optical bandgap is also discussed. Time resolved photoluminescence shows multi-exponential decay with 21 psec. and 49{plus minus}3 psec. lifetimes, suggesting that composition micro- fluctuations may be present in Cd0.16Zn0.84O film. We also report on crystallographic and optical properties of CdZnO/ZnO multiple quantum wells.

Published
2006

35. Optical Characterization of Zn1-xCdxO Alloys Grown by Molecular-Beam Epitaxy

Author

Buyanova, Irina A., Wang, Xingjun, Chen, Weimin M., Izadifard, Morteza, Norton, David, Pearton, Steve J., Osinsky, Andrei V., Dong, Jianwei, and Dabiran, Amir M.

Abstract

We have carried out comprehensive optical studies to evaluate structural and bandgap properties of Zn1-xCdxO alloys with x {less than or equal to} 0.17 grown by molecular beam epitaxy. High crystalline quality of the alloys was concluded from cathodoluminescence measurements. Based on absorption and reflectance measurements, the compositional dependence of the bandgap energy of ZnCdO, estimated without taking into account excitonic effects, was found to follow the trend Eg(x)=3.28- 2.23x+0.45x2. Degradation in the alloy quality due to possible phase separation was found to cause deviations from this trend, evident from a more rapid red shift of the absorption edge. Effects of Cd incorporation on the variation of the bandgap energies with temperature are also discussed.

Published
2006

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