@Article{strathprints84031,
author = {Cameron, Douglas and Coulon, Pierre-Marie and Fairclough, Simon and Kusch, Gunnar and Edwards, Paul R. and Susilo, Norman and Wernicke, Tim and Kneissl, Michael and Oliver, Rachel A. and Shields, Philip A. and Martin, Robert W.},
journal = {Nano Letters},
title = {Core-shell nanorods as ultraviolet light emitting diodes},
year = {2023},
issn = {1530-6992},
month = {February},
number = {4},
pages = {1451--1458},
volume = {23},
abstract = {Existing barriers to efficient deep UV LEDs may be reduced or overcome by moving away from conventional planar growth and towards three dimensional nanostructuring. Nanorods have the potential for enhanced doping, reduced dislocation densities, improved light extraction efficiency and quantum wells free from the quantum confined Stark effect. Here, we demonstrate a hybrid top-down/bottom-up approach to creating highly uniform AlGaN core-shell nanorods on sapphire repeatable on wafer scales. Our GaN-free design avoids self-absorption of the quantum well emission, while preserving electrical functionality. The effective junctions formed by doping of both the n-type cores and p-type caps were studied using nanoprobing experiments where we find low turn on voltages, strongly rectifying behaviours and significant electron beam induced currents. Timeresolved cathodoluminescence measurements find short carrier liftetimes consistent with reduced polarisation fields. Our results show nanostructuring to be a promising route to deep-UV emitting LEDs, achievable using commercially compatible methods.},
doi = {10.1021/acs.nanolett.2c04826},
keywords = {nanorods, LEDs, UV LED, nanowire, core-shell, AIGaN, semiconductors, electron microscopy, Optics. Light, Atomic and Molecular Physics, and Optics},
url = {https://doi.org/10.1021/acs.nanolett.2c04826},
}

@Article{strathprints80115,
author = {Cameron, Douglas and Edwards, Paul R. and Mehnke, Frank and Kusch, Gunnar and Sulmoni, Luca and Schilling, Marcel and Wernicke, Tim and Kneissl, Michael and Martin, Robert W.},
journal = {Applied Physics Letters},
title = {The influence of threading dislocations propagating through an {AlGaN UVC LED}},
year = {2022},
issn = {0003-6951},
month = {March},
pages = {162101},
volume = {120},
abstract = {During the epitaxy of AlGaN on sapphire for deep UV emitters, significant lattice mismatch leads to highly strained heterojunctions and the formation of threading dislocations. Combining cathodoluminescence, electron beam induced current and x-ray microanalysis reveal that dislocations with a screw component permeate through a state-of-the-art UVC LED heterostructure into the active region and perturb their local environment in each layer as growth progresses. In addition to acting as non-radiative recombination centers, these dislocations encourage high point defect densities and three-dimensional growth within their vicinity. We find that these point defects can add parasitic recombination pathways and compensate intentional dopants.},
doi = {10.1063/5.0086034},
keywords = {electron beam-induced current (EBIC), cathodoluminescence (CL), WDX, AlGaN, light emitting diode (LED), scanning electron microscopy (SEM), Physics, Condensed Matter Physics, Electronic, Optical and Magnetic Materials},
url = {https://strathprints.strath.ac.uk/80115/},
}

@Article{strathprints76920,
author = {Spasevski, Lucia and Buse, Ben and Edwards, Paul R. and Hunter, Daniel A. and Enslin, Johannes and Foronda, Humberto M. and Wernicke, Tim and Mehnke, Frank and Parbrook, Peter J. and Kneissl, Michael and Martin, Robert W.},
journal = {Microscopy and Microanalysis},
title = {Quantification of trace-level silicon doping in {AlₓGa₁₋ₓN} films using wavelength-dispersive {X}-ray microanalysis},
year = {2021},
issn = {1431-9276},
month = {August},
pages = {696--704},
volume = {27},
abstract = {Wavelength dispersive X-ray (WDX) spectroscopy was used to measure silicon atom concentrations in the range 35-100 ppm (corresponding to (3-9) {$\times$}1018 cm-3) in doped AlₓGa₁₋ₓN films using an electron probe microanalyser also equipped with a cathodoluminescence (CL) spectrometer. Doping with Si is the usual way to produce the n-type conducting layers that are critical in GaN and AlₓGa₁₋ₓN-based devices such as LEDs and laser diodes. Previously we have shown excellent agreement for Mg dopant concentrations in p-GaN measured by WDX with values from the more widely used technique of secondary ion mass spectrometry (SIMS). However, a discrepancy between these methods has been reported when quantifying the n-type dopant, silicon. We identify the cause of discrepancy as inherent sample contamination and propose a way to correct this using a calibration relation. This new approach, using a method combining data derived from SIMS measurements on both GaN and AlₓGa₁₋ₓN samples, provides the means to measure the Si content in these samples with account taken of variations in the ZAF corrections. This method presents a cost effective and time saving way to measure the Si doping and can also benefit from simultaneously measuring other signals, such as CL and electron channeling contrast imaging.},
doi = {10.1017/S1431927621000568},
keywords = {wavelength dispersive x-ray, cathodoluminescence, Wide band-gap semiconductors, Physics, Instrumentation},
url = {https://doi.org/10.1017/S1431927621000568},
}

@Article{strathprints70583,
author = {S. Walde and S. Hagedorn and P.-M. Coulon and A. Mogilatenko and C. Netzel and J. Weinrich and N. Susilo and E. Ziffer and L. Matiwe and C. Hartmann and G. Kusch and A. Alasmari and G. Naresh-Kumar and C. Trager-Cowan and T. Wernicke and T. Straubinger and M. Bickermann and R. W. Martin and P. A. Shields and M. Kneissl and M. Weyers},
journal = {Journal of Crystal Growth},
title = {{AlN} overgrowth of nano-pillar-patterned sapphire with different offcut angle by metalorganic vapor phase epitaxy},
year = {2020},
month = {November},
pages = {125343},
volume = {531},
abstract = {We present overgrowth of nano-patterned sapphire with different offcut angles by metalorganic vapor phase epitaxy. Hexagonal arrays of nano-pillars were prepared via Displacement Talbot Lithography and dry-etching. 6.6 µm crack-free and fully coalesced AlN was grown on such substrates. Extended defect analysis comparing X-ray diffraction, electron channeling contrast imaging and selective defect etching revealed a threading dislocation density of about 10⁹ cm⁻². However, for c-plane sapphire offcut of 0.2° towards m direction the AlN surface shows step bunches with a height of 10 nm. The detrimental impact of these step bunches on subsequently grown AlGaN multi-quantum-wells is investigated by cathodoluminescence and transmission electron microscopy. By reducing the sapphire offcut to 0.1° the formation of step bunches is successfully suppressed. On top of such a sample an AlGaN-based UVC LED heterostructure is realized emitting at 265 nm and showing an emission power of 0.81 mW at 20 mA (corresponds to an external quantum efficiency of 0.86 %).},
keywords = {metal organic vapor phase epitaxy, nitrides, sapphire, light emitting diodes, Physics, Materials Chemistry, Condensed Matter Physics},
url = {https://strathprints.strath.ac.uk/70583/},
}

@article{strathprints74889,
volume = {117},
number = {22},
month = {November},
title = {Electrical properties of (11-22) Si:AlGaN layers at high Al contents grown by metal-organic vapor phase epitaxy},
year = {2020},
doi = {10.1063/5.0031468},
journal = {Applied Physics Letters},
keywords = {Hall measurements, electrical properties, partial pressures, Physics, Physics and Astronomy(all)},
url = {https://doi.org/10.1063/5.0031468},
issn = {0003-6951},
abstract = {In this work, the growth and conductivity of semipolar AlxGa1?xN:Si with (11-22) orientation are investigated. AlxGa1?xN:Si (x = 0.60 {$\pm$} 0.03 and x = 0.80 {$\pm$} 0.02) layers were grown with different SiH4 partial pressures, and the electrical properties were determined using Hall measurements at room temperature. The aluminum mole fraction was measured by wavelength dispersive x-ray spectroscopy and x-ray diffraction, and the Si-concentration was measured by wavelength dispersive x-ray spectroscopy and secondary ion mass spectroscopy. Layer resistivities as low as 0.024 ? cm for x = 0.6 and 0.042 ? cm for x = 0.8 were achieved. For both aluminum mole fractions, the resistivity exhibits a minimum with the increasing Si concentration, which can be explained by compensation due to the formation of cation vacancy complexes at high doping levels. The onset of self-compensation occurs at larger estimated Si concentrations for larger Al contents.},
author = {Foronda, Humberto M. and Hunter, Daniel A. and Pietsch, Mike and Sulmoni, Luca and Muhin, Anton and Graupeter, Sarina and Susilo, Norman and Schilling, Marcel and Enslin, Johannes and Irmscher, Klaus and Martin, Robert W. and Wernicke, Tim and Kneissl, Michael}
}

@article{strathprints74344,
volume = {53},
number = {50},
month = {September},
title = {The 2020 UV emitter roadmap},
year = {2020},
doi = {10.1088/1361-6463/aba64c},
journal = {Journal of Physics D: Applied Physics},
keywords = {AlGaN, InGaN, UV-LED, light emitting diodes, ultraviolet, Physics, Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Acoustics and Ultrasonics, Surfaces, Coatings and Films},
url = {https://doi.org/10.1088/1361-6463/aba64c},
issn = {0022-3727},
abstract = {Solid state UV emitters have many advantages over conventional UV sources. The (Al,In,Ga)N material system is best suited to produce LEDs and laser diodes from 400 nm down to 210 nm-due to its large and tuneable direct band gap, n- and p-doping capability up to the largest bandgap material AlN and a growth and fabrication technology compatible with the current visible InGaN-based LED production. However AlGaN based UV-emitters still suffer from numerous challenges compared to their visible counterparts that become most obvious by consideration of their light output power, operation voltage and long term stability. Most of these challenges are related to the large bandgap of the materials. However, the development since the first realization of UV electroluminescence in the 1970s shows that an improvement in understanding and technology allows the performance of UV emitters to be pushed far beyond the current state. One example is the very recent realization of edge emitting laser diodes emitting in the UVC at 271.8 nm and in the UVB spectral range at 298 nm. This roadmap summarizes the current state of the art for the most important aspects of UV emitters, their challenges and provides an outlook for future developments.},
author = {Amano, Hiroshi and Collazo, Ram{\'o}n and De Santi, Carlo and Einfeldt, Sven and Funato, Mitsuru and Glaab, Johannes and Hagedorn, Sylvia and Hirano, Akira and Hirayama, Hideki and Ishii, Ryota and Kashima, Yukio and Kawakami, Yoichi and Kirste, Ronny and Kneissl, Michael and Martin, Robert and Mehnke, Frank and Meneghini, Matteo and Ougazzaden, Abdallah and Parbrook, Peter J and Rajan, Siddharth and Reddy, Pramod and R{\"o}mer, Friedhard and Ruschel, Jan and Sarkar, Biplab and Scholz, Ferdinand and Schowalter, Leo J and Shields, Philip and Sitar, Zlatko and Sulmoni, Luca and Wang, Tao and Wernicke, Tim and Weyers, Markus and Witzigmann, Bernd and Wu, Yuh-Renn and Wunderer, Thomas and Zhang, Yuewei}
}

@article{strathprints74728,
volume = {891},
number = {1},
month = {August},
title = {Advances in electron channelling contrast imaging and electron backscatter diffraction for imaging and analysis of structural defects in the scanning electron microscope},
year = {2020},
doi = {10.1088/1757-899X/891/1/012023},
journal = {IOP Conference Series: Materials Science and Engineering},
keywords = {scanning electron microscopy, contrast imaging, imaging techniques, Physics, Materials Science(all), Engineering(all), Physics and Astronomy(all)},
url = {https://doi.org/10.1088/1757-899X/891/1/012023},
issn = {1757-899X},
abstract = {In this article we describe the scanning electron microscopy (SEM) techniques of electron channelling contrast imaging and electron backscatter diffraction. These techniques provide information on crystal structure, crystal misorientation, grain boundaries, strain and structural defects on length scales from tens of nanometres to tens of micrometres. Here we report on the imaging and analysis of dislocations and sub-grains in nitride semiconductor thin films (GaN and AlN) and tungsten carbide-cobalt (WC-Co) hard metals. Our aim is to illustrate the capability of these techniques for investigating structural defects in the SEM and the benefits of combining these diffraction-based imaging techniques.},
author = {Trager-Cowan, C. and Alasmari, A. and Avis, W. and Bruckbauer, J. and Edwards, P. R. and Hourahine, B. and Kraeusel, S. and Kusch, G. and Jablon, B. M. and Johnston, R. and Martin, R. W. and McDermott, R. and Naresh-Kumar, G. and Nouf-Allehiani, M. and Pascal, E. and Thomson, D. and Vespucci, S. and Mingard, K. and Parbrook, P. J. and Smith, M. D. and Enslin, J. and Mehnke, F. and Kneissl, M. and Kuhn, C. and Wernicke, T. and Knauer, A. and Hagedorn, S. and Walde, S. and Weyers, M. and Coulon, P-M and Shields, P. A. and Zhang, Y. and Jiu, L. and Gong, Y. and Smith, R. M. and Wang, T. and Winkelmann, A.}
}

@Article{strathprints71512,
author = {Carol Trager-Cowan and Aeshah Alasmari and William Avis and Jochen Bruckbauer and Paul R. Edwards and Gergely Ferenczi and Benjamin Hourahine and Almpes Kotzai and Simon Kraeusel and Gunnar Kusch and Robert W. Martin and Ryan McDermott and Naresh Gunasekar and M. Nouf-Allehiani and Elena Pascal and David Thomson and Stefano Vespucci and Matthew David Smith and Peter J. Parbrook and Johannes Enslin and Frank Mehnke and Christian Kuhn and Tim Wernicke and Michael Kneissl and Sylvia Hagedorn and Arne Knauer and Sebastian Walde and Markus Weyers and Pierre-Marie Coulon and Philip Shields and J. Bai and Y. Gong and Ling Jiu and Y. Zhang and Richard Smith and Tao Wang and Aimo Winkelmann},
journal = {Semiconductor Science and Technology},
title = {Structural and luminescence imaging and characterisation of semiconductors in the scanning electron microscope},
year = {2020},
month = {February},
pages = {054001},
volume = {35},
abstract = {The scanning electron microscopy techniques of electron backscatter diffraction (EBSD), electron channelling contrast imaging (ECCI) and hyperspectral cathodoluminescence imaging (CL) provide complementary information on the structural and luminescence properties of materials rapidly and non-destructively, with a spatial resolution of tens of nanometres. EBSD provides crystal orientation, crystal phase and strain analysis, whilst ECCI is used to determine the planar distribution of extended defects over a large area of a given sample. CL reveals the influence of crystal structure, composition and strain on intrinsic luminescence and/or reveals defect-related luminescence. Dark features are also observed in CL images where carrier recombination at defects is non-radiative. The combination of these techniques is a powerful approach to clarifying the role of crystallography and extended defects on a materials' light emission properties. Here we describe the EBSD, ECCI and CL techniques and illustrate their use for investigating the structural and light emitting properties of UV-emitting nitride semiconductor structures. We discuss our investigations of the type, density and distribution of defects in GaN, AlN and AlGaN thin films and also discuss the determination of the polarity of GaN nanowires.},
keywords = {EBSD, nitride, scanning electron microscopy, Physics, Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering, Condensed Matter Physics},
url = {https://strathprints.strath.ac.uk/71512/},
}

@Article{strathprints69913,
author = {C. Trager-Cowan and A. Alasmari and W. Avis and Jochen Bruckbauer and P. R. Edwards and B. Hourahine and S. Kraeusel and G. Kusch and R. Johnston and G. Naresh-Kumar and R. W. Martin and M. Nouf-Allehiani and E. Pascal and L. Spasevski and D. Thomson and S. Vespucci and P. J. Parbrook and M. D. Smith and J. Enslin and F. Mehnke and M. Kneissl and C. Kuhn and T. Wernicke and S. Hagedorn and S. Walde and M. Weyers and P.-M. Coulon and P. A. Shields and Y. Zhang and L. Jiu and Y. P. Gong and R. M. Smith and T. Wang and A. Winkelmann},
title = {The scanning electron microscope as a flexible tool for investigating the properties of {UV}-emitting nitride semiconductor thin films},
journal = {Photonics Research},
year = {2019},
volume = {7},
number = {11},
pages = {B73--B82},
month = {September},
abstract = {In this article we describe the scanning electron microscopy techniques of electron backscatter diffraction (EBSD), electron channelling contrast imaging (ECCI), wavelength dispersive X-ray spectroscopy (WDX) and cathodoluminescence (CL) hyperspectral imaging. We present our recent results on the use of these non-destructive techniques to obtain information on the topography, crystal misorientation, defect distributions, composition, doping and light emission from a range of UV emitting nitride semiconductor structures. We aim to illustrate the developing capability of each of these techniques for understanding the properties of UV emitting nitride semiconductors, and the benefits were appropriate, in combining the techniques.},
keywords = {scanning electron microscopy, electron backscatter diffraction, non-destructive techniques, UV emitting nitride semiconductors, Physics, Atomic and Molecular Physics, and Optics},
url = {https://strathprints.strath.ac.uk/69913/},
}

@Article{strathprints71494,
author = {Johannes Enslin and Tim Wernicke and Anna Lobanova and Gunnar Kusch and Lucia Spasevski and Tolga Teke and Bettina Belde and Robert W. Martin and Roman Talalaev and Michael Kneissl},
title = {Indium incorporation in quaternary Inx Aly Ga1-x-y N for UVB-LEDs},
journal = {Japanese Journal of Applied Physics},
year = {2019},
volume = {58},
number = {SC},
pages = {SC1004},
month = {April},
abstract = {Consistent studies of the quaternary composition are rare as it is impossible to fully determine the quaternary composition by X-ray diffraction or deduce it from that of ternary alloys. In this paper we determined the quaternary composition by wavelength dispersive X-ray spectroscopy of Inx Aly layers grown by metal organic vapor phase epitaxy. Further insights explaining the peculiarities of Inx Aly Ga1-x-yN growth in a showerhead reactor were gained by simulations of the precursor decomposition, gas phase adduct formation and indium incorporation including desorption. The measurements and simulations agree very well showing that the indium incorporation in a range from 0\% to 2\% is limited by desorption which is enhanced by the compressive strain to the relaxed Al0.5Ga0.5N buffer layer as well as indium incorporation into AlN particles forming in the gas phase. Utilizing Inx Aly Ga1-x-yN layers containing 2\% of indium for multiple quantum wells (MQWs), it was possible to show an almost five times higher photoluminescence intensity of InAlGaN MQWs in comparison to AlGaN MQWs.},
keywords = {quaternary composition, X-ray spectroscopy, X-ray diffraction, UVB, ultraviolet light, light emitting diodes, LEDs, Physics, Physics and Astronomy(all)},
url = {https://strathprints.strath.ac.uk/71494/},
}

@Article{strathprints67321,
author = {Gunnar Kusch and Johannes Enslin and Lucia Spasevski and Tolga Teke and Tim Wernicke and Paul R. Edwards and Michael Kneissl and Robert W. Martin},
title = {Influence of InN and AlN concentration on the compositional inhomogeneity and formation of InN-rich regions in InxAlyGa1-x-yN},
journal = {Japanese Journal of Applied Physics},
year = {2019},
volume = {58},
pages = {SCCB18},
month = {March},
abstract = {The application of quaternary InxAlyGa1-x-yN active regions is a promising path towards high efficiency UVB-LEDs. For the utilisation of InxAlyGa1-x-yN, detailed knowledge of the interplay between growth parameters, adatom incorporation, optical and structural properties is crucial. We investigated the influence of the TMAl and TMIn flux on the composition and luminescence properties of InxAlyGa1-x-yN layers by multi-mode scanning electron microscopy. We found that varying the molar TMIn flow from 0 to 17.3 µmol/min led to an InN concentration between 0% and 3.2% and an emission energy between 4.17 eV and 3.75 eV. The variation of the molar TMAl flow from 3.5 to 35.4 µmol/min resulted in a AlN composition between 7.8% and 30.7% with an emission energy variation between 3.6 eV and 4.1 eV. Cathodoluminescence hyperspectral imaging provided evidence for the formation of nanoscale InN-rich regions. Analysing the emission properties of these InN-rich regions showed that their emission energy is inhomogeneous and varies by ~150 meV. We provide evidence that the formation of these InN-rich regions is highly dependent on the AlN and InN composition of the layer and that their formation will strongly affect the performance of InxAlyGa1-x-yN LEDs.},
keywords = {high efficiency UVB-LEDs, composition, luminescence, cathodoluminescence hyperspectral imaging, Physics, Physics and Astronomy(all)},
url = {https://strathprints.strath.ac.uk/67321/}
}

@Article{strathprints59282,
author = {Gunnar Kusch and Frank Mehnke and Johannes Enslin and Paul R Edwards and Tim Wernicke and Michael Kneissl and Robert W Martin},
title = {Analysis of doping concentration and composition in wide bandgap {AlGaN:Si} by wavelength dispersive {X}-ray spectroscopy},
journal = {Semiconductor Science and Technology},
year = {2017},
volume = {32},
number = {3},
pages = {035020},
month = {February},
abstract = {Detailed knowledge of the dopant concentration and composition of wide band gap AlxGa1?xN layers is of crucial importance for the fabrication of ultra violet (UV) light emitting diodes (LEDs). This paper demonstrates the capabilities of wavelength dispersive X-ray (WDX) spectroscopy in accurately determining these parameters and compares the results with those from high resolution X-ray diffraction (HR-XRD) and secondary ion mass spectrometry (SIMS). WDX spectroscopy has been carried out on different silicon-doped wide bandgap AlxGa1?xN samples (x between 0.80 and 1). This study found a linear increase in the Si concentration with the SiH4/group-III ratio, measuring Si concentrations between 3{$\times$}1018 cm?3 and 2.8{$\times$}1019 cm?3, while no direct correlation between the AlN composition and the Si incorporation ratio was found. Comparison between the composition obtained by WDX and by HR-XRD showed very good agreement in the range investigated, while comparison of the donor concentration between WDX and SIMS found only partial agreement, which we attribute to a number of effects.},
keywords = {dopant concentration, ultra violet light emitting diodes, wavelength dispersive X-ray spectroscopy, high resolution X-ray diffraction, doping concentrations, semiconductors, dopant composition, Physics, Physics and Astronomy(all)},
url = {http://strathprints.strath.ac.uk/59282/}
}

@Article{strathprints54134,
author = {Gunnar Kusch and M. Nouf-Allehiani and Frank Mehnke and Christian Kuhn and Paul R. Edwards and Tim Wernicke and Arne Knauer and Viola Kueller and G. Naresh-Kumar and Markus Weyers and Michael Kneissl and Carol Trager-Cowan and Robert W. Martin},
title = {Spatial clustering of defect luminescence centers in {Si}-doped low resistivity {Al₀.₈₂Ga₀.₁₈N}},
journal = {Applied Physics Letters},
year = {2015},
volume = {107},
number = {7},
pages = {072103},
month = {August},
abstract = {A series of Si-doped AlN-rich AlGaN layers with low resistivities was characterized by a combination of nanoscale imaging techniques. Utilizing the capability of scanning electron microscopy to reliably investigate the same sample area with different techniques, it was possible to determine the effect of doping concentration, defect distribution, and morphology on the luminescence properties of these layers. Cathodoluminescence shows that the dominant defect luminescence depends on the Si-doping concentration. For lower doped samples, the most intense peak was centered between 3.36 eV and 3.39 eV, while an additional, stronger peak appears at 3 eV for the highest doped sample. These peaks were attributed to the (VIII-ON)2? complex and the VIII3? vacancy, respectively. Multimode imaging using cathodoluminescence, secondary electrons, electron channeling contrast, and atomic force microscopy demonstrates that the luminescence intensity of these peaks is not homogeneously distributed but shows a strong dependence on the topography and on the distribution of screw dislocations.},
keywords = {nanoscale imaging, cathodoluminescence, multimode imaging, Physics, Physics and Astronomy (miscellaneous)},
url = {http://strathprints.strath.ac.uk/54134/}
}

@Article{strathprints50638,
author = {G. Naresh-Kumar and A. Vilalta-Clemente and S. Pandey and D. Skuridina and H. Behmenburg and P. Gamarra and G. Patriarche and I. Vickridge and M. A. di Forte-Poisson and P. Vogt and M. Kneissl and M. Morales and P. Ruterana and A. Cavallini and D. Cavalcoli and C. Giesen and M. Heuken and C. Trager-Cowan},
title = {Multicharacterization approach for studying InAl(Ga)N/Al(Ga)N/GaN heterostructures for high electron mobility transistors},
journal = {AIP Advances},
year = {2014},
volume = {4},
number = {12},
pages = {127101},
month = {December},
abstract = {We report on our multi?pronged approach to understand the structural and electrical properties of an InAl(Ga)N(33nm barrier)/Al(Ga)N(1nm interlayer)/GaN(3{\ensuremath{\mu}}m)/AlN(100nm)/Al2O3 high electron mobility transistor (HEMT) heterostructure grown by metal organic vapor phase epitaxy (MOVPE). In particular we reveal and discuss the role of unintentional Ga incorporation in the barrier and also in the interlayer. The observation of unintentional Ga incorporation by using energy dispersive X?ray spectroscopy analysis in a scanning transmission electron microscope is supported with results obtained for samples with a range of AlN interlayer thicknesses grown under both the showerhead as well as the horizontal type MOVPE reactors. Poisson?Schr{\"o}dinger simulations show that for high Ga incorporation in the Al(Ga)N interlayer, an additional triangular well with very small depth may be exhibited in parallel to the main 2?DEG channel. The presence of this additional channel may cause parasitic conduction and severe issues in device characteristics and processing. Producing a HEMT structure with InAlGaN as the barrier and AlGaN as the interlayer with appropriate alloy composition may be a possible route to optimization, as it might be difficult to avoid Ga incorporation while continuously depositing the layers using the MOVPE growth method. Our present work shows the necessity of a multicharacterization approach to correlate structural and electrical properties to understand device structures and their performance.},
keywords = {Ga incorporation, III-V semiconductors, Rutherford backscattering, Physics, Electronic, Optical and Magnetic Materials, Physics and Astronomy (miscellaneous)},
url = {http://strathprints.strath.ac.uk/50638/}
}