Special Issue "Micro- and Nanotechnology of Wide Bandgap Semiconductors"

A special issue of Electronics (ISSN 2079-9292). This special issue belongs to the section "Semiconductor Devices".

Deadline for manuscript submissions: closed (31 October 2020).

Special Issue Editors

Prof. Dr. Anna B. Piotrowska
Website
Guest Editor
Lukasiewicz Research Network, Institute of Microelectronics and Photonics (SBL-IMiF), 02-668 Warszawa, Poland
Interests: Micro- and nanotechnology of wide bandgap semiconductors; GaN-based devices RF and high power application; II-VI oxide semiconductors for sensors
Prof. Dr. Eliana Kamińska
Website
Guest Editor
Institute of High Pressure Physics Unipress, Al. Prymasa Tysiaclecia 98, 01-142 Warsaw, Poland
Interests: GaN; ZnO; oxides; nitrides
Special Issues and Collections in MDPI journals
Prof. Dr. Wojtek Wojtasiak
Website
Guest Editor
Institute of Radioelectronics and Multimedia Techniques, Faculty of Electronics and Information Technology, Warsaw University of Technology, Poland
Interests: power amplifiers; AlGaN / GaN HEMT technology; microwave systems

Special Issue Information

Dear Colleagues,

Owing to their unique characteristics—direct wide bandgap energy, large breakdown field, and excellent electron transport properties, including operation in high-temperature environments and low sensitivity to ionizing radiation gallium nitride (GaN) and related group III-nitride heterostructures have proven to be enabling materials for advanced optoelectronic and electronic devices and systems. Today they are widely used in short-wavelength light-emitting diodes (LEDs) and laser diodes (LDs), high-performing radar, wireless telecommunications, as well as ‘green’ power electronics. Impressive progress in GaN technology over the last 25 years has been driven by a continuously growing need for more advanced systems and new challenges continue to arise and need to be solved. The lighting industry, RF defense industry, and 5G mmWave telecommunication systems are driving forces for further intense research in order to reach the full potential of GaN-based semiconductors. In the literature, there are a number of review papers and publications reporting technology progress and indicating future trends.

In this Special Issue of Electronics, 12 papers will be published, the majority of them are focused materials and process technology of GaN-based devices fabricated on native GaN substrates. The specific topics include the following: GaN single crystalline substrates for electronic devices by ammonothermal and HVPE methods, drift layers by HVPE, MOVPE, and MBE, advances in ion implantation of GaN and related materials, high-pressure processing (lattice reconstruction) of ion-implanted GaN (Mg and Be), novel metallization schemes for ohmic contacts, thermal issues in GaN HEMTs, AlGaN/GaN HEMTs on native substrates, laser diodes based on MOVPE and MBE epitaxy including vertically integrated devices with tunnel junctions, monolithic green-blue and red-green-blue LED structures for highly efficient displays, external cavity laser diodes for quantum technologies applications, porous GaN for supercondensators, and III-nitride nanowires for LEDs.

Prof. Dr. Anna B. Piotrowska
Prof. Dr. Eliana Kamińska
Prof. Dr. Wojtek Wojtasiak
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Electronics is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • GaN
  • III-nitride heterostructures
  • native GaN substrates
  • HVPE
  • MOVPE
  • MBE
  • ion implantation
  • device processing
  • LEDs
  • laser diodes
  • RF HEMTs
  • vertical electronic devices

Published Papers (8 papers)

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Research

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Open AccessArticle
Influence of Growth Polarity Switching on the Optical and Electrical Properties of GaN/AlGaN Nanowire LEDs
Electronics 2021, 10(1), 45; https://doi.org/10.3390/electronics10010045 - 29 Dec 2020
Abstract
For the development and application of GaN-based nanowire structures, it is crucial to understand their fundamental properties. In this work, we provide the nano-scale correlation of the morphological, electrical, and optical properties of GaN/AlGaN nanowire light emitting diodes (LEDs), observed using a combination [...] Read more.
For the development and application of GaN-based nanowire structures, it is crucial to understand their fundamental properties. In this work, we provide the nano-scale correlation of the morphological, electrical, and optical properties of GaN/AlGaN nanowire light emitting diodes (LEDs), observed using a combination of spatially and spectrally resolved cathodoluminescence spectroscopy and imaging, electron beam-induced current microscopy, the nano-probe technique, and scanning electron microscopy. To complement the results, the photo- and electro-luminescence were also studied. The interpretation of the experimental data was supported by the results of numerical simulations of the electronic band structure. We characterized two types of nanowire LEDs grown in one process, which exhibit top facets of different shapes and, as we proved, have opposite growth polarities. We show that switching the polarity of nanowires (NWs) from the N- to Ga-face has a significant impact on their optical and electrical properties. In particular, cathodoluminescence studies revealed quantum wells emissions at about 3.5 eV, which were much brighter in Ga-polar NWs than in N-polar NWs. Moreover, the electron beam-induced current mapping proved that the p–n junctions were not active in N-polar NWs. Our results clearly indicate that intentional polarity inversion between the n- and p-type parts of NWs is a potential path towards the development of efficient nanoLED NW structures. Full article
(This article belongs to the Special Issue Micro- and Nanotechnology of Wide Bandgap Semiconductors)
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Open AccessArticle
Growth Uniformity in Selective Area Epitaxy of AlGaN/GaN Heterostructures for the Application in Semiconductor Devices
Electronics 2020, 9(12), 2129; https://doi.org/10.3390/electronics9122129 - 12 Dec 2020
Abstract
The design of modern semiconductor devices often requires the fabrication of three-dimensional (3D) structures to integrate microelectronic components with photonic, micromechanical, or sensor systems within one semiconductor substrate. It is a technologically challenging task, as a strictly defined profile of the device structure [...] Read more.
The design of modern semiconductor devices often requires the fabrication of three-dimensional (3D) structures to integrate microelectronic components with photonic, micromechanical, or sensor systems within one semiconductor substrate. It is a technologically challenging task, as a strictly defined profile of the device structure is obligatory. This can be achieved either by chemical etching or selective deposition on a masked substrate. In this paper, the growth uniformity of AlGaN/GaN heterostructures during selective-area metalorganic vapour-phase epitaxy (SA-MOVPE) was studied. Such structures are typically used in order to fabricate high-electron-mobility transistors (HEMT). The semiconductor material was deposited through 200 μm long stripe-shaped open windows in a SiO2 mask on GaN/sapphire templates. The window width was varied from 5 μm to 160 μm, whereas mask width separating particular windows varied from 5 μm to 40 μm. The experiment was repeated for three samples differing in GaN layer thickness: 150 nm, 250 nm, and 500 nm. Based on theoretical models of the selective growth, a sufficiently uniform thickness of epitaxially grown AlGaN/GaN heterostructure has been achieved by selecting the window half-width that is smaller than the diffusion length of the precursor molecules. A Ga diffusion length of 15 μm was experimentally extracted by measuring the epitaxial material agglomeration in windows in the dielectric mask. Measurements were conducted while using optical profilometry. Full article
(This article belongs to the Special Issue Micro- and Nanotechnology of Wide Bandgap Semiconductors)
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Open AccessArticle
Influence of Si Substrate Preparation Procedure on Polarity of Self-Assembled GaN Nanowires on Si(111): Kelvin Probe Force Microscopy Studies
Electronics 2020, 9(11), 1904; https://doi.org/10.3390/electronics9111904 - 13 Nov 2020
Abstract
The growth of GaN nanowires having a polar, wurtzite structure on nonpolar Si substrates raises the issue of GaN nanowire polarity. Depending on the growth procedure, coexistence of nanowires with different polarities inside one ensemble has been reported. Since polarity affects the optical [...] Read more.
The growth of GaN nanowires having a polar, wurtzite structure on nonpolar Si substrates raises the issue of GaN nanowire polarity. Depending on the growth procedure, coexistence of nanowires with different polarities inside one ensemble has been reported. Since polarity affects the optical and electronic properties of nanowires, reliable methods for its control are needed. In this work, we use Kelvin probe force microscopy to assess the polarity of GaN nanowires grown by plasma-assisted Molecular Beam Epitaxy on Si(111) substrates. We show that uniformity of the polarity of GaN nanowires critically depends on substrate processing prior to the growth. Nearly 18% of nanowires with reversed polarity (i.e., Ga-polar) were found on the HF-etched substrates with hydrogen surface passivation. Alternative Si substrate treatment steps (RCA etching, Ga-triggered deoxidation) were tested. However, the best results, i.e., purely N-polar ensemble of nanowires, were obtained on Si wafers thermally deoxidized in the growth chamber at ~1000 °C. Interestingly, no mixed polarity was found for GaN nanowires grown under similar conditions on Si(111) substrates with a thin AlOy buffer layer. Our results show that reversal of nanowires’ polarity can be prevented by growing them on a chemically uniform substrate surface, in our case on clean, in situ formed SiNx or ex situ deposited AlOy buffers. Full article
(This article belongs to the Special Issue Micro- and Nanotechnology of Wide Bandgap Semiconductors)
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Open AccessArticle
Demonstration of AlGaN/GaN MISHEMT on Si with Low-Temperature Epitaxy Grown AlN Dielectric Gate
Electronics 2020, 9(11), 1858; https://doi.org/10.3390/electronics9111858 - 05 Nov 2020
Cited by 1
Abstract
AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MISHEMT) with a low-temperature epitaxy (LTE)-grown single crystalline AlN gate dielectric were demonstrated for the first time and the post-gate annealing effects at 400 °C were studied. The as-deposited LTE-AlN MISHEMT showed a maximum drain current (IDmax) [...] Read more.
AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MISHEMT) with a low-temperature epitaxy (LTE)-grown single crystalline AlN gate dielectric were demonstrated for the first time and the post-gate annealing effects at 400 °C were studied. The as-deposited LTE-AlN MISHEMT showed a maximum drain current (IDmax) of 708 mA/mm at a gate bias of 4 V and a maximum extrinsic transconductance (gmmax) of 129 mS/mm. The 400 °C annealed MISHEMT exhibited an increase of 15% in gmmax, an order of magnitude reduction in reverse gate leakage and about a 3% suppression of drain current (ID) collapse. The increase of gmmax by post-gate annealing is consistent with the increase of 2DEG mobility. The suppression of ID collapse and the reduction of gate leakage current is attributed to the reduction of interface state density (5.0 × 1011 cm−2eV−1) between the AlN/GaN interface after post-gate annealing at 400 °C. This study demonstrates that LTE grown AlN is a promising alternate material as gate dielectric for GaN-based MISHEMT application. Full article
(This article belongs to the Special Issue Micro- and Nanotechnology of Wide Bandgap Semiconductors)
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Open AccessArticle
Vertical Integration of Nitride Laser Diodes and Light Emitting Diodes by Tunnel Junctions
Electronics 2020, 9(9), 1481; https://doi.org/10.3390/electronics9091481 - 10 Sep 2020
Abstract
We demonstrate the applications of tunnel junctions (TJs) for new concepts of monolithic nitride-based multicolor light emitting diode (LED) and laser diode (LD) stacks. The presented structures were grown by plasma-assisted molecular beam epitaxy (PAMBE) on GaN bulk crystals. We demonstrate a stack [...] Read more.
We demonstrate the applications of tunnel junctions (TJs) for new concepts of monolithic nitride-based multicolor light emitting diode (LED) and laser diode (LD) stacks. The presented structures were grown by plasma-assisted molecular beam epitaxy (PAMBE) on GaN bulk crystals. We demonstrate a stack of four LDs operated at pulse mode with emission wavelength of 453 nm. The output power of 1.1 W and high slope efficiency of 2.3 W/A is achieved for devices without dielectric mirrors. Atomically flat surface after the epitaxy of four LD stack and low dislocation density is measured as a result of proper TJ design with optimized doping level. The strain compensation design with InGaN waveguides and AlGaN claddings is shown to be crucial to avoid cracking and lattice relaxation of the 5 µm thick structure. Vertical connection of n-LDs allows for cascade emission of photons and increases the quantum efficiency n-times. The two-color (blue and green) LEDs are demonstrated. Application of TJs simplifies device processing, reducing the need for applications of p-type contact. The key factor enabling demonstration of such devices is hydrogen-free PAMBE technology, in which activation of buried p-type layers is not necessary. Full article
(This article belongs to the Special Issue Micro- and Nanotechnology of Wide Bandgap Semiconductors)
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Open AccessArticle
Characterization of Self-Heating Process in GaN-Based HEMTs
Electronics 2020, 9(8), 1305; https://doi.org/10.3390/electronics9081305 - 13 Aug 2020
Cited by 1
Abstract
Thermal characterization of modern microwave power transistors such as high electron-mobility transistors based on gallium nitride (GaN-based HEMTs) is a critical challenge for the development of high-performance new generation wireless communication systems (LTE-A, 5G) and advanced radars (active electronically scanned array (AESA)). This [...] Read more.
Thermal characterization of modern microwave power transistors such as high electron-mobility transistors based on gallium nitride (GaN-based HEMTs) is a critical challenge for the development of high-performance new generation wireless communication systems (LTE-A, 5G) and advanced radars (active electronically scanned array (AESA)). This is especially true for systems operating with variable-envelope signals where accurate determination of self-heating effects resulting from strong- and fast-changing power dissipated inside transistor is crucial. In this work, we have developed an advanced measurement system based on DeltaVGS method with implemented software enabling accurate determination of device channel temperature and thermal resistance. The methodology accounts for MIL-STD-750-3 standard but takes into account appropriate specific bias and timing conditions. Three types of GaN-based HEMTs were taken into consideration, namely commercially available GaN-on-SiC (CGH27015F and TGF2023-2-01) and GaN-on-Si (NPT2022) devices, as well as model GaN-on-GaN HEMT (T8). Their characteristics of thermal impedance, thermal time constants and thermal equivalent circuits were presented. Knowledge of thermal equivalent circuits and electro–thermal models can lead to improved design of GaN HEMT high-power amplifiers with account of instantaneous temperature variations for systems using variable-envelope signals. It can also expand their range of application. Full article
(This article belongs to the Special Issue Micro- and Nanotechnology of Wide Bandgap Semiconductors)
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Review

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Open AccessReview
High Pressure Processing of Ion Implanted GaN
Electronics 2020, 9(9), 1380; https://doi.org/10.3390/electronics9091380 - 26 Aug 2020
Cited by 1
Abstract
It is well known that ion implantation is one of the basic tools for semiconductor device fabrication. The implantation process itself damages, however, the crystallographic lattice of the semiconductor. Such damage can be removed by proper post-implantation annealing of the implanted material. Annealing [...] Read more.
It is well known that ion implantation is one of the basic tools for semiconductor device fabrication. The implantation process itself damages, however, the crystallographic lattice of the semiconductor. Such damage can be removed by proper post-implantation annealing of the implanted material. Annealing also allows electrical activation of the dopant and creates areas of different electrical types in a semiconductor. However, such thermal treatment is particularly challenging in the case of gallium nitride since it decomposes at relatively low temperature (~800 °C) at atmospheric pressure. In order to remove the implantation damage in a GaN crystal structure, as well as activate the implanted dopants at ultra-high pressure, annealing process is proposed. It will be described in detail in this paper. P-type GaN implanted with magnesium will be briefly discussed. A possibility to analyze diffusion of any dopant in GaN will be proposed and demonstrated on the example of beryllium. Full article
(This article belongs to the Special Issue Micro- and Nanotechnology of Wide Bandgap Semiconductors)
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Open AccessReview
GaN Single Crystalline Substrates by Ammonothermal and HVPE Methods for Electronic Devices
Electronics 2020, 9(9), 1342; https://doi.org/10.3390/electronics9091342 - 19 Aug 2020
Abstract
Recent results of GaN bulk growth performed in Poland are presented. Two technologies are described in detail: halide vapor phase epitaxy and basic ammonothermal. The processes and their results (crystals and substrates) are demonstrated. Some information about wafering procedures, thus, the way from [...] Read more.
Recent results of GaN bulk growth performed in Poland are presented. Two technologies are described in detail: halide vapor phase epitaxy and basic ammonothermal. The processes and their results (crystals and substrates) are demonstrated. Some information about wafering procedures, thus, the way from as-grown crystal to an epi-ready wafer, are shown. Results of other groups in the world are briefly presented as the background for our work. Full article
(This article belongs to the Special Issue Micro- and Nanotechnology of Wide Bandgap Semiconductors)
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