TopGaN Ltd.

Warsaw, Poland

TopGaN Ltd.

Warsaw, Poland
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Marona L.,Polish Academy of Sciences | Perlin P.,Polish Academy of Sciences | Perlin P.,TopGaN Ltd. | Czernecki R.,Polish Academy of Sciences | And 8 more authors.
Applied Physics Letters | Year: 2011

We performed a systematic secondary ions mass spectroscopy (SIMS) study of dopant impurities in life-time stressed InGaN laser devices in order to investigate the main degradation mechanism that is observed in nitride laser diodes. A continuous wave (cw) current density of 3 kA/cm2 was applied to InGaN laser diodes over an extended period of time and we observed the characteristic square root degradation of optical power. We compared the SIMS profiles of Mg, H, and Si impurities in the aged devices and observe that the impurities are remarkably stable over 10 000 h of cw operation. Nor is there any SIMS evidence of p-contact metals penetrating into the semiconductor material. Thus our SIMS results are contrary to what one would expect for impurity diffusion causing the observed square root degradation characteristic. © 2011 American Institute of Physics.

Domagala J.Z.,Polish Academy of Sciences | Morelhao S.L.,University of Sao Paulo | Sarzynski M.,Polish Academy of Sciences | Mazdziarz M.,Polish Institute of Fundamental Technological Research | And 2 more authors.
Journal of Applied Crystallography | Year: 2016

Epitaxy of semiconductors is a process of tremendous importance in applied science and in the optoelectronics industry. The control of defects introduced during epitaxial growth is a key point in manufacturing devices of high efficiency and durability. In this work, it is demonstrated how useful hybrid reflections are for the study of epitaxial structures with anisotropic strain gradients due to patterned substrates. High accuracy in detecting and distinguishing elastic and plastic relaxations is one of the greatest advantages of measuring this type of reflection, as well as the fact that the method can be exploited in a symmetric reflection geometry on a commercial high-resolution diffractometer. © 2016 International Union of Crystallography.

Perlin P.,TopGaN Ltd. | Perlin P.,Polish Academy of Sciences | Marona L.,Polish Academy of Sciences | Holc K.,TopGaN Ltd. | And 11 more authors.
Applied Physics Express | Year: 2011

We demonstrate the operation of high-power InGaN laser diode "mini-arrays" consisting of three or five stripes in a common p-contact configuration and compare the results with a single stripe emitter. We observed the following sequence of maximum output powers: 1.1W for a single emitter, 2.5W for a three emitter array, and 0.55W for a five emitter array. The devices emitted light at 408-412nm wavelength range. The most promising high-power laser diode design turned out to be a three stripe solution. The five stripe "mini-array" suffers from overheating, which causes the device to thermally roll-over at relatively low optical power. In addition to the high power operation, the three stripe device has good spectral characteristics accompanied by very reasonable differential efficiency making it a good candidate for ultra-high optical power systems like laser projectors. © 2011 The Japan Society of Applied Physics.

Turski H.,Polish Academy of Sciences | Siekacz M.,Polish Academy of Sciences | Siekacz M.,Top GaN Ltd. | Wasilewski Z.R.,University of Waterloo | And 5 more authors.
Journal of Crystal Growth | Year: 2013

In this work we study the peculiar role of gallium and nitrogen atoms in the growth of InGaN by Plasma Assisted Molecular Beam Epitaxy (PAMBE). We investigate growth of InGaN layers on vicinal GaN (0001) substrates. Indium incorporation as a function of gallium and nitrogen fluxes was examined. We propose a microscopic model of InGaN growth by PAMBE postulating different indium adatom incorporation mechanisms on two nonequivalent atomic step edges of wurtzite crystal. The role of gallium and nitrogen fluxes during the growth of InGaN layers is discussed. © 2013 Elsevier B.V. All rights reserved.

Sawicka M.,Polish Academy of Sciences | Sawicka M.,TopGaN Ltd. | Turski H.,Polish Academy of Sciences | Siekacz M.,Polish Academy of Sciences | And 9 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

The homoepitaxial growth of m-plane (11̄00) GaN was investigated by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions. The surface morphologies as a function of sample miscut were studied, providing evidence for a strong growth anisotropy that is a consequence of the anisotropy of Ga adatom diffusion barriers on the m-plane surface recently calculated ab initio. We found that substrate miscut toward [0001̄] implies a step flow toward 112̄6̄ while substrate miscut toward [0001] causes formation of atomic steps either perpendicular or parallel to the [0001] direction, under N-rich conditions at 730 °C. We describe the growth conditions for achieving atomically flat m-plane GaN layers with parallel atomic steps. © 2011 American Physical Society.

Piotrzkowski R.,Polish Academy of Sciences | Litwin-Staszewska E.,Polish Academy of Sciences | Grzanka S.,Polish Academy of Sciences | Grzanka S.,Top GaN Ltd.
Applied Physics Letters | Year: 2011

Modern optoelectronic devices are often based on wide-bandgap semiconductors such as GaN. In such cases the current injecting contacts are usually nonlinear, especially for p-type materials. Using the standard transmission line method (TLM), which gives satisfactory results in linear cases, characterization of nonlinear contacts can lead to serious ambiguities. In this Letter, we derive exact formulas permitting to extract the current-voltage characteristics of the non-linear metal-semiconductor contact from measurements performed on standard TLM pattern, as well as to simulate behavior of such pattern for given model contact characteristic. The application of this generalized TLM method is illustrated on the example of Ni/Au contacts on p-GaN © 2011 American Institute of Physics.

Kudrawiec R.,Wroclaw University of Technology | Gladysiewicz M.,Wroclaw University of Technology | Janicki L.,Wroclaw University of Technology | Misiewicz J.,Wroclaw University of Technology | And 6 more authors.
Applied Physics Letters | Year: 2012

Contactless electroreflectance (CER) has been applied to study the Fermi-level position on c-plane GaN surface in Van Hoof structures grown by molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE). A clear CER resonance followed by strong Franz-Keldysh oscillation (FKO) of various periods was clearly observed for the series of samples of different thicknesses (30, 50, and 70 nm) of undoped GaN layer. The built-in electric field in this layer has been determined from the period of GaN-related FKO. A good agreement between the calculated and measured electric fields has been found for the Fermi-level located ∼0.4 and ∼0.3 eV below the conduction band for the MBE and MOVPE samples, respectively. © 2012 American Institute of Physics.

Muziol G.,Polish Academy of Sciences | Turski H.,Polish Academy of Sciences | Siekacz M.,Polish Academy of Sciences | Siekacz M.,TopGaN Ltd | And 7 more authors.
Applied Physics Letters | Year: 2013

The optical gain spectra of InGaN-based multiple-quantum-well (MQW) laser diodes (LDs) grown by plasma-assisted molecular beam epitaxy are compared for different emission wavelengths. Two AlGaN cladding free LDs with similar epitaxial structures but with different In compositions in MQW were grown to study the dependence of material gain on lasing wavelength. As the emission wavelength increased from 432 to 458 nm, the differential modal gain decreased from 5.7 to 4.7 cm/kA, and the optical losses increased from 40 to 46 cm -1 resulting in an increase in threshold current density. This dependence is attributed to lower optical mode confinement of LD emitting at longer wavelength. We found a strong decrease of confinement factor with increasing wavelength. © 2013 AIP Publishing LLC.

Kamyczek P.,Wroclaw University of Technology | Placzek-Popko E.,Wroclaw University of Technology | Kolkovsky Vl.,TU Dresden | Grzanka S.,TopGaN Ltd. | And 3 more authors.
Journal of Applied Physics | Year: 2012

In the present study, the electrical and optical properties of deep defects in p-i-n GaN junction and AlGaN/GaN heterojunction are investigated by means of the deep level transient spectroscopy (DLTS), Laplace DLTS, and electroluminescence (EL) techniques. We demonstrate that in both structures the yellow luminescence (YL) is a dominant band in the EL spectra recorded at room temperature. We correlate the YL band with the minority DLTS peaks observed at about 370 K. A gallium vacancy-related defect seems to be a probable candidate as to the origin of the defect. Another dominant majority peak observed in the DLTS studies was concluded to be linked with a donor-like defect in the upper half of the bandgap. The origin of the defect is discussed. © 2012 American Institute of Physics.

Kafar A.,Polish Academy of Sciences | Stanczyk S.,Polish Academy of Sciences | Targowski G.,TopGaN Ltd. | Oto T.,Kyoto University | And 5 more authors.
Applied Physics Express | Year: 2013

We demonstrate blue-violet InGaN superluminescent diodes (SLDs) with bent-waveguide (j-shape) geometry, emitting optical power exceeding 200mW for SLD with 1-mm-long waveguide. The adopted j-shape geometry prevents devices from lasing, even at the highest applied currents (450 mA). However, high-resolution measurements reveal the appearance of spectral ripples at currents on the order of 250 mA. The maximum output power increases with the waveguide length. © 2013 The Japan Society of Applied Physics.

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