Editorial

3 pages, 178 KiB

Open AccessEditorial

Micro- and Nanotechnology of Wide-Bandgap Semiconductors

by Anna B. Piotrowska, Eliana Kamińska and Wojciech Wojtasiak

Electronics 2021, 10(4), 507; https://doi.org/10.3390/electronics10040507 - 22 Feb 2021

Cited by 1 | Viewed by 1908

Gallium Nitride and Related Wide-Bandgap Semiconductors (WBS) have constantly received a great amount of attention in recent years [...] Full article

(This article belongs to the Special Issue Micro- and Nanotechnology of Wide Bandgap Semiconductors)

Research

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20 pages, 6152 KiB

Open AccessArticle

Influence of Growth Polarity Switching on the Optical and Electrical Properties of GaN/AlGaN Nanowire LEDs

by Anna Reszka, Krzysztof P. Korona, Stanislav Tiagulskyi, Henryk Turski, Uwe Jahn, Slawomir Kret, Rafał Bożek, Marta Sobanska, Zbigniew R. Zytkiewicz and Bogdan J. Kowalski

Electronics 2021, 10(1), 45; https://doi.org/10.3390/electronics10010045 - 29 Dec 2020

Cited by 3 | Viewed by 3408

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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15 pages, 34077 KiB

Open AccessArticle

Growth Uniformity in Selective Area Epitaxy of AlGaN/GaN Heterostructures for the Application in Semiconductor Devices

by Michał Stępniak, Mateusz Wośko, Joanna Prażmowska-Czajka, Andrzej Stafiniak, Dariusz Przybylski and Regina Paszkiewicz

Electronics 2020, 9(12), 2129; https://doi.org/10.3390/electronics9122129 - 12 Dec 2020

Cited by 5 | Viewed by 2306

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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13 pages, 3119 KiB

Open AccessArticle

Influence of Si Substrate Preparation Procedure on Polarity of Self-Assembled GaN Nanowires on Si(111): Kelvin Probe Force Microscopy Studies

by Marta Sobanska, Núria Garro, Kamil Klosek, Ana Cros and Zbigniew R. Zytkiewicz

Electronics 2020, 9(11), 1904; https://doi.org/10.3390/electronics9111904 - 13 Nov 2020

Cited by 1 | Viewed by 1936

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 AlO_y 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 SiN_x or ex situ deposited AlO_y buffers. Full article

(This article belongs to the Special Issue Micro- and Nanotechnology of Wide Bandgap Semiconductors)

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8 pages, 1928 KiB

Open AccessArticle

Demonstration of AlGaN/GaN MISHEMT on Si with Low-Temperature Epitaxy Grown AlN Dielectric Gate

by Matthew Whiteside, Subramaniam Arulkumaran, Yilmaz Dikme, Abhinay Sandupatla and Geok Ing Ng

Electronics 2020, 9(11), 1858; https://doi.org/10.3390/electronics9111858 - 05 Nov 2020

Cited by 6 | Viewed by 2887

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 (I_Dmax) [...] 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 (I_Dmax) of 708 mA/mm at a gate bias of 4 V and a maximum extrinsic transconductance (g_mmax) of 129 mS/mm. The 400 °C annealed MISHEMT exhibited an increase of 15% in g_mmax, an order of magnitude reduction in reverse gate leakage and about a 3% suppression of drain current (I_D) collapse. The increase of g_mmax by post-gate annealing is consistent with the increase of 2DEG mobility. The suppression of I_D 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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11 pages, 3236 KiB

Open AccessArticle

Vertical Integration of Nitride Laser Diodes and Light Emitting Diodes by Tunnel Junctions

by Marcin Siekacz, Grzegorz Muziol, Henryk Turski, Mateusz Hajdel, Mikolaj Żak, Mikolaj Chlipała, Marta Sawicka, Krzesimir Nowakowski-Szkudlarek, Anna Feduniewicz-Żmuda, Julita Smalc-Koziorowska, Szymon Stańczyk and Czeslaw Skierbiszewski

Electronics 2020, 9(9), 1481; https://doi.org/10.3390/electronics9091481 - 10 Sep 2020

Cited by 16 | Viewed by 3279

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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14 pages, 4201 KiB

Open AccessArticle

Characterization of Self-Heating Process in GaN-Based HEMTs

by Daniel Gryglewski, Wojciech Wojtasiak, Eliana Kamińska and Anna Piotrowska

Electronics 2020, 9(8), 1305; https://doi.org/10.3390/electronics9081305 - 13 Aug 2020

Cited by 17 | Viewed by 4209

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 DeltaV_GS 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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11 pages, 27959 KiB

Open AccessReview

High Pressure Processing of Ion Implanted GaN

by Kacper Sierakowski, Rafal Jakiela, Boleslaw Lucznik, Pawel Kwiatkowski, Malgorzata Iwinska, Marcin Turek, Hideki Sakurai, Tetsu Kachi and Michal Bockowski

Electronics 2020, 9(9), 1380; https://doi.org/10.3390/electronics9091380 - 26 Aug 2020

Cited by 42 | Viewed by 4993

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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12 pages, 4844 KiB

Open AccessReview

GaN Single Crystalline Substrates by Ammonothermal and HVPE Methods for Electronic Devices

by Karolina Grabianska, Piotr Jaroszynski, Aneta Sidor, Michal Bockowski and Malgorzata Iwinska

Electronics 2020, 9(9), 1342; https://doi.org/10.3390/electronics9091342 - 19 Aug 2020

Cited by 22 | Viewed by 4672

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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