Hiroto Sekiguchi  Kei Kato  Jo Tanaka  Akihiko Kikuchi  Katsumi Kishino 《physica status solidi (a)》2008,205(5):1067-1069

We report the fabrication of GaN/AlGaN nanocolumn LEDs on n‐(111) Si substrates by RF‐MBE for the first time. Clear diode characteristics with a turn‐on voltage of 4 V and an ultraviolet emission spectrum with a peak wavelength of 354 nm were observed at room temperature. When the Al composition of p‐Al_x Ga_1–x N was changed from 8.8% to 25.1%, the high Al content led a narrowing of the FWHM compared withthat for low Al contents due to the suppression of carrier overflow. We measured the electroluminescence (EL) under dc and pulsed operations. The integrated EL intensity under the pulsed operation was 3 times as strong as that under the dc operation at 100 mA due to the reduced generation of heat. The thermal resistance was estimated to be 40 °C/W from the EL peak wavelength difference between the dc and pulsed operations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

E. Dimakis  A. Yu. Nikiforov  C. Thomidis  L. Zhou  D. J. Smith  J. Abell  C.‐K. Kao  T. D. Moustakas 《physica status solidi (a)》2008,205(5):1070-1073

Near‐ultraviolet light emitting diodes (LEDs), based on one monolayer thick InN/GaN multiple quantum wells, were grown by radio‐frequency plasma‐assisted molecular beam epitaxy. The active region was grown at 685 °C, a temperature where the growth of thick InN layers is not possible. High resolution transmission electron microscopy revealed that the InN well layers were grown pseudomorphically in between the GaN barriers and were characterized by well defined interfaces and uniform thickness. The LED structures exhibited electroluminescence emission at 384 nm, with a FWHM of about 14 nm. The peak emission wavelength was independent of the injection current, indicating the absence of quantum confined Stark effect in these structures. Output optical power of 0.84 mW was measured at 200 mA in a bare die configuration. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

T. D. Moustakas  Tao Xu  C. Thomidis  A. Yu Nikiforov  Lin Zhou  David J. Smith 《physica status solidi (a)》2008,205(11):2560-2565

In this paper we discuss the growth of InN, GaN and InGaN QDs by MBE on either GaN or AlN templates. InN QDs on GaN templates were found to occur without an InN wetting layer, a result consistent with the large lattice mismatch of 11% between InN and GaN. Self‐assembled GaN QDs were grown on AlN templates, using the modified Stranski‐Krastanov mode of growth. The microstructure and the size distribution of such QDs in a single layer or a superlattice structure were investigated by electron microscopy and atomic force microscopy. Finally, the self assembly of InGaN QDs on GaN templates using the Stranski‐Krastanov mode and the applications of such QDs to blue‐green LEDs are addressed. The results indicate that InGaN / GaN multiple quantum dots (MQDs) are highly strained and their emission at low injection is red shifted with respect to that of a single layer of QDs due to quantum confined Stark effect. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

Shunsuke Ishizawa  Hiroto Sekiguchi  Akihiko Kikuchi  Katsumi Kishino 《physica status solidi b》2007,244(6):1815-1819

For the application of GaN nanocolumns, one of the most important issues is to control their shapes and positions. We demonstrated a selective RF‐MBE growth of GaN nanocolumns using patterned Al thin pre‐deposited layers on a substrate via their nitridation. As the nanocolumns were grown at the edge of the nitrided Al patterns, a possibility of controlling the shape and the position of nanocolumns was suggested. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

Alan S. de Menezes  Adenilson O. dos Santos  Juliana M. A. Almeida  Jos R. R. Bortoleto  Mnica A. Cotta  Srgio L. Morelho  Lisandro P. Cardoso 《physica status solidi b》2009,246(3):544-547

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J. Y. Lim  J. D. Song  W. J. Choi  H. S. Yang 《physica status solidi (a)》2010,207(2):391-395

The purpose of this work is to find optimal conditions for the growth of three‐dimensional (3D) InAs islands on (2 × 1) (001) Si substrate using modified Stranski–Krastanow (S–K) method. From the analysis of atomic‐force‐microscopy (AFM) images and reflection‐high‐energy‐electron‐diffraction (RHEED) patterns, we have found that InAs islands can be grown on Si when the growth temperature is in the range of 370–430 °C and also when In‐injection of more than three periods is used. At the growth temperature of 390 °C and In‐injection of four periods, uniform distribution of islands with the highest density of about 600 /µm² were obtained. The average width and height of these islands were 36.1 ± 9.2 nm and 6.2 ± 2.0 nm, respectively.  相似文献   

    

Victor H. Mndez‐García  I. Martínez‐Velis  J. S. Rojas‐Ramirez  R. Contreras‐Guerrero  M. Ramírez‐Lopez  J. Hernandez‐Rosas  G. Garcia‐Lian  A. Yu. Gorbatchev  L. Zamora‐Peredo  M. Lpez‐Lpez 《physica status solidi (a)》2009,206(5):836-841

The molecular beam epitaxial (MBE) growth of InAs nanostructures on GaAs(631)‐oriented substrates is studied by photoluminescence (PL) and photoreflectance spectroscopy (PR). First, a corrugated surface conformed by regularly spaced grooves aligned along the [ 93] azimuth was formed by the GaAs homoepitaxial growth on the (631) substrate. On this template, we proceeded with the deposition of InAs at several thicknesses in the range of 1 to 4.5 monolayers (MLs). An atomic force microscopy (AFM) analysis of samples without GaAs capping, revealed that assemblage of QDs occurs only after the deposition of the equivalent to ∼1.9 ML of InAs. On these samples, we observed changes on the PR line‐shape in the near‐bandgap GaAs region linked to the quantity of InAs deposited. The intensity of the built in electric fields was correlated with the strain state at the heterointerface, as a consequence of the self induced piezoelectric effect, typical from high index surfaces. On the other hand, when the samples were capped with a 100 Å thick GaAs layer, strong emission of the nanostructures occurs even for deposited quantities of InAs as low as 1 ML. Since for this InAs thickness the self‐assemblage of QDs is not observed, the optical transitions observed were associated with the optical emission of self assembled semiconductor quantum wires, promoted by surface diffusion anisotropy, characteristic of the (631) plane. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

G. Cherkashinin  V. Lebedev  R. Wagner  I. Cimalla  O. Ambacher 《physica status solidi b》2006,243(7):1713-1717

The responsivity and the decay time of AlGaN solar blind UV‐detectors have been studied. The photodetectors have shown a good spectral responsivity in a narrow spectral range (220 < λ < 300 nm) and a short time response with the best estimated characteristic time constant of τ ∼ 30 ms measured at room temperature. Possible mechanisms responsible for the persistent photoconductivity (PPC) effect in Al_xGa_1–xN (x = 0.51) are analyzed. A shape of the spectral response as a function of the applied voltage is analyzed in the frameworks of the space‐charge limited current model. It has been shown that the main source of PPC is traps above the Fermi level. PPC occurs when the density of free carriers equals the density of the traps. The model attributing PPC to the spatial separation of the photoexcited electrons and holes by the macroscopic potential barrier is not supported by our photocurrent studies. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

K. R. Wang  L. W. Tu  S. J. Lin  Y. L. Chen  Z. W. Jiang  M. Chen  C. L. Hsiao  K. H. Cheng  J. W. Yeh  S. K. Chen 《physica status solidi b》2006,243(7):1461-1467

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J. Heffernan  M. Kauer  K. Johnson  C. Zellweger  S. E. Hooper  V. Bousquet 《physica status solidi (a)》2005,202(5):868-874

We report progress in the development of InGaN multiple quantum well laser diodes grown by MBE. Lasers were grown by gas‐source MBE using ammonia as the source of nitrogen. Devices were grown on both GaN template substrates with dry‐etched laser facets, and on low dislocation density free‐standing GaN substrates where cleaved laser facets are possible. We have achieved a minimum threshold current density of ∼11 kA cm^–2 on templates and ∼7 kA cm^–2 on free‐standing GaN. On GaN substrates we have achieved room temperature operation with a pulsed duty cycle of 10%. Further optimisation of the device is required to reduce thermal effects and achieve CW operation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献