Research

14 pages, 12717 KiB

Open AccessArticle

Analysis of the Effect of Copper Doping on the Optoelectronic Properties of Indium Oxide Thin Films and the Thermoelectric Properties of an In₂O₃/Pt Thermocouple

by Yantao Liu, Tao Lin, Rong Huang, Jiahao Shi and Sui Chen

Crystals 2024, 14(1), 78; https://doi.org/10.3390/cryst14010078 - 13 Jan 2024

Viewed by 914

Abstract

The detection and real-time monitoring of temperature parameters are important, and indium oxide-based thin film thermocouples can be integrated on the surface of heaters because they operate normally under harsh conditions and provide accurate online temperature monitoring. The higher stability and appropriate optical [...] Read more.

The detection and real-time monitoring of temperature parameters are important, and indium oxide-based thin film thermocouples can be integrated on the surface of heaters because they operate normally under harsh conditions and provide accurate online temperature monitoring. The higher stability and appropriate optical and electrical properties of In₂O₃ make it very suitable as an electrode material for thermocouple sensors. This work demonstrates that copper doping can alter the optical and electrical properties of In₂O₃ films and regulate the output performance of thermocouples. Copper-doped In₂O₃ thin films were prepared using the magnetron co-sputtering method. The doping concentration of Cu was controlled using direct current (DC) power. An In₂O₃/Pt thermocouple sensor was prepared, and the optoelectronic and thermocouple properties were adjusted by changing the copper doping content. The thickness valve of the thin film sample was 300 nm. The results of the X-ray diffraction suggested that the structure of the doped In₂O₃ thin films was cubic. The results of the energy-dispersive X-ray analysis revealed that Cu was doped into the In₂O₃ thin films. All deposited films were n-type semiconductor materials according to Hall effect testing. The 4.09 at% Cu-doped thin films possessed the highest resistivity (30.2 × 10⁻³ Ω·cm), a larger carrier concentration (3.72 × 10²⁰ cm⁻³), and the lowest carrier mobility (0.56 cm²V⁻¹s⁻¹). The optical band gap decreased from 3.76 to 2.71 eV with an increase in the doping concentration, and the transmittance of the film significantly reduced. When the DC power was increased, the variation range of Seebeck coefficient for the In₂O₃/Pt thermocouple was 152.1–170.5 μV/°C, and the range of thermal output value was 91.4–102.4 mV. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductor Materials, Devices and Systems)

► Show Figures

Figure 1

13 pages, 3248 KiB

Open AccessArticle

NiO/Ga₂O₃ Vertical Rectifiers of 7 kV and 1 mm² with 5.5 A Forward Conduction Current

by Jian-Sian Li, Hsiao-Hsuan Wan, Chao-Ching Chiang, Timothy Jinsoo Yoo, Fan Ren, Honggyu Kim and Stephen J. Pearton

Crystals 2023, 13(12), 1624; https://doi.org/10.3390/cryst13121624 - 23 Nov 2023

Viewed by 1019

Abstract

In this study, we present the fabrication and characterization of vertically oriented NiO/β polymorph n-Ga₂O₃/n+ Ga₂O₃ heterojunction rectifiers featuring a substantial area of 1 mm². A dual-layer SiN_X/SiO₂ dielectric field plate [...] Read more.

In this study, we present the fabrication and characterization of vertically oriented NiO/β polymorph n-Ga₂O₃/n+ Ga₂O₃ heterojunction rectifiers featuring a substantial area of 1 mm². A dual-layer SiN_X/SiO₂ dielectric field plate edge termination was employed to increase the breakdown voltage (V_B). These heterojunction rectifiers exhibit remarkable simultaneous achievement of high breakdown voltage and substantial conducting currents. In particular, the devices manifest V_B of 7 kV when employing a 15 µm thick drift layer doping concentration of 8.8 × 10¹⁵ cm⁻³, concurrently demonstrating a forward current of 5.5 A. The thick drift layer is crucial in obtaining high V_B since similar devices fabricated on 10 µm thick epilayers had breakdown voltages in the range of 3.6–4.0 kV. Reference devices fabricated on the 15 µm drift layers had V_B of 5 kV. The breakdown is still due to leakage current from tunneling and thermionic emission and not from avalanche breakdown. An evaluation of the power figure-of-merit, represented by V_B²/R_ON, reveals a value of 9.2 GW·cm⁻², where R_ON denotes the on-state resistance, measuring 5.4 mΩ·cm². The Coff was 4 nF/cm², leading to an R_ON × C_off of 34 ps and F_CO of 29 GHz. The turn-on voltage for these rectifiers was ~2 V. This exceptional performance surpasses the theoretical unipolar one-dimensional (1D) limit of both SiC and GaN, underscoring the potential of β-Ga₂O₃ for forthcoming generations of high-power rectification devices. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductor Materials, Devices and Systems)

► Show Figures

Figure 1

9 pages, 3672 KiB

Open AccessArticle

Hexagonal Nanocrystal Growth of Mg or Zn from Incorporation in GaN Powders Obtained through Pyrolysis of a Viscous Complex Compound and Its Nitridation

by Erick Gastellóu, Rafael García, Ana M. Herrera, Antonio Ramos, Godofredo García, Gustavo A. Hirata, José A. Luna, Roberto C. Carrillo, Jorge A. Rodríguez, Mario Robles and Yani D. Ramírez

Crystals 2023, 13(10), 1421; https://doi.org/10.3390/cryst13101421 - 25 Sep 2023

Viewed by 623

Abstract

Hexagonal nanocrystals were obtained from Zn-doped GaN powders and Mg-doped GaN powders, which were synthesized via pyrolysis of a viscous complex compound, followed by its nitridation. XRD showed well-defined peaks for hexagonal GaN with an average crystal size of 21.3 nm. Scanning electron [...] Read more.

Hexagonal nanocrystals were obtained from Zn-doped GaN powders and Mg-doped GaN powders, which were synthesized via pyrolysis of a viscous complex compound, followed by its nitridation. XRD showed well-defined peaks for hexagonal GaN with an average crystal size of 21.3 nm. Scanning electron microscopy showed an amorphous and porous appearance in surface morphology, which could be related to the combustion process. Energy-dispersive spectroscopy characterization showed contributions of gallium, nitrogen, and small traces of Zn and Mg in the GaN samples. TEM showed the presence of well-defined hexagonal nanocrystals with an area of 75.9 nm² for the Zn-doped GaN powders and an area of 67.7 nm² for the Mg-doped GaN powders. The photoluminescence spectra showed an emission energy of 2.8 eV (431.5 nm) for the Zn-doped GaN powders, while the Mg-doped GaN powders showed energies in the range from 2.7 eV to 2.8 eV (460.3 nm–443.9 nm). The Raman scattering showed spectra where the vibration modes A₁(TO), E₁(TO), and E₂(High) could be observed, which are characteristic of hexagonal GaN. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductor Materials, Devices and Systems)

► Show Figures

Figure 1

11 pages, 1812 KiB

Open AccessArticle

A Fast Recovery SiC TED MOS MOSFET with Schottky Barrier Diode (SBD)

by Hongyu Cheng, Wenmao Li, Peiran Wang, Jianguo Chen, Qing Wang and Hongyu Yu

Crystals 2023, 13(4), 650; https://doi.org/10.3390/cryst13040650 - 10 Apr 2023

Viewed by 1771

Abstract

Achieving low conduction loss and good channel mobility is crucial for SiC MOSFETs. However, basic planar SiC MOSFETs provide challenges due to their high density of interface traps and significant gate-to-drain capacitance. In order to enhance the reverse recovery property of the device, [...] Read more.

Achieving low conduction loss and good channel mobility is crucial for SiC MOSFETs. However, basic planar SiC MOSFETs provide challenges due to their high density of interface traps and significant gate-to-drain capacitance. In order to enhance the reverse recovery property of the device, a Schottky barrier diode (SBD) was added to the source contact area, the top of the current spreading region, of a trench-etched double-diffused SiC MOS (TED MOS). Two types of SBD structures were optimized to improve the electrical properties using 3D simulation software, “TCAD Silvaco”. During reverse recovery simulation, the carriers of the device were withdrawn from the SBD, indicating that the new design was effective. It also showed that the recovery properties of the new design depended on temperature, carrier lifetime, and the work functions of metals. All the new designs were evaluated in various circumstances to determine the trend. Ultimately, in high-speed switching circuits, the SiC TED MOS with SBD structure efficiently boosted switching speed, while reducing switching loss. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductor Materials, Devices and Systems)

► Show Figures

Figure 1

10 pages, 3095 KiB

Open AccessArticle

Pressure Sensing of Symmetric Defect Photonic Crystals Composed of Superconductor and Semiconductor in Low-Temperature Environment

by Haiyang Hu, Xiaoling Chen, Miaomiao Zhao, Liyan Wang, Ming Fang and Dong Zhao

Crystals 2023, 13(3), 471; https://doi.org/10.3390/cryst13030471 - 09 Mar 2023

Viewed by 958

Abstract

We theoretically investigate the defect mode transmittance of light waves in superconductor–semiconductor photonic crystals and its pressure-sensing dependence. The photonic crystal is composed of alternating superconducting and semiconducting slabs and a defect locates at the center of this structure. Two trapezoid waveguides are [...] Read more.

We theoretically investigate the defect mode transmittance of light waves in superconductor–semiconductor photonic crystals and its pressure-sensing dependence. The photonic crystal is composed of alternating superconducting and semiconducting slabs and a defect locates at the center of this structure. Two trapezoid waveguides are fixed at both sides of the crystal, which induces the hydrostatic pressure applied and beams transmitted simultaneously. The resonant wavelength variation in the defect mode is directly proportional to the pressure applied on the system in the near-IR region, which can be utilized for linear pressure sensors in the cryogenic environment. Pressure sensitivity reaches a high value of 2.6 nm/GPa, which is higher than that in the study based on the reflection spectra. The sensitivity coefficient may be modulated by the environment temperature as well. This study has potential regarding pressure-light-wave sensors. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductor Materials, Devices and Systems)

► Show Figures

Figure 1

10 pages, 2688 KiB

Open AccessArticle

Temperature Sensing Based on Defect Mode of One-Dimensional Superconductor-Semiconductor Photonic Crystals

by Huisheng Wei, Xiaoling Chen, Dong Zhao, Miaomiao Zhao, Yang Wang and Pu Zhang

Crystals 2023, 13(2), 302; https://doi.org/10.3390/cryst13020302 - 12 Feb 2023

Cited by 5 | Viewed by 1783

Abstract

Based on the transfer-matrix method, we theoretically explore the transmission and reflection properties of light waves in a one-dimensional defective photonic crystal composed of superconductor (HgBa₂Ca₂Cu₃O_8+δ) and semiconductor (GaAs) layers. The [...] Read more.

Based on the transfer-matrix method, we theoretically explore the transmission and reflection properties of light waves in a one-dimensional defective photonic crystal composed of superconductor (HgBa₂Ca₂Cu₃O_8+δ) and semiconductor (GaAs) layers. The whole system is centrosymmetric and can generate a defect transmission peak in the photonic band gap. We study the effect of the temperature on the defect mode. Results obtained show that the defect mode shifts to the lower frequency regions as the value of the environmental temperature increases, and the resonance of the defect mode can be strengthened further as the number of periods increases. In addition, our findings reveal that the central wavelength of the defect mode increases with the increase in the environmental temperature and it presents a nearly linear relationship between the central wavelength of the defect mode and the temperature in cryogenic environments. Therefore, we can use the temperature response of the defect mode to detect the temperature. It is hoped that this study has potential applications for the development of cryogenic sensors with high sensitivity. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductor Materials, Devices and Systems)

► Show Figures

Figure 1

10 pages, 2501 KiB

Open AccessArticle

Simulation of High Breakdown Voltage, Improved Current Collapse Suppression, and Enhanced Frequency Response AlGaN/GaN HEMT Using A Double Floating Field Plate

by Peiran Wang, Chenkai Deng, Hongyu Cheng, Weichih Cheng, Fangzhou Du, Chuying Tang, Chunqi Geng, Nick Tao, Qing Wang and Hongyu Yu

Crystals 2023, 13(1), 110; https://doi.org/10.3390/cryst13010110 - 07 Jan 2023

Cited by 5 | Viewed by 2557

Abstract

In this paper, DC, transient, and RF performances among AlGaN/GaN HEMTs with a no field plate structure (basic), a conventional gate field plate structure (GFP), and a double floating field plate structure (2FFP) were studied by utilizing SILVACO ATLAS 2D device technology computer-aided [...] Read more.

In this paper, DC, transient, and RF performances among AlGaN/GaN HEMTs with a no field plate structure (basic), a conventional gate field plate structure (GFP), and a double floating field plate structure (2FFP) were studied by utilizing SILVACO ATLAS 2D device technology computer-aided design (TCAD). The peak electric fields under the gate in drain-side can be alleviated effectively in 2FFP devices, compared with basic and GFP devices, which promotes the breakdown voltage (BV) and suppresses the current collapse phenomenon. As a result, the ON-resistance increase caused by the current collapse phenomena is dramatically suppressed in 2FFP ~19.9% compared with GFP ~49.8% when a 1 ms duration pre-stress was applied with V_ds = 300 V in the OFF-state. Because of the discontinuous FP structure, more electric field peaks appear at the edge of the FFP stacks, which leads to a higher BV of ~454.4 V compared to the GFP ~394.3 V and the basic devices ~57.6 V. Moreover, the 2FFP structure performs lower a parasitic capacitance of C_gs = 1.03 pF and C_gd = 0.13 pF than those of the GFP structure (i.e., C_gs = 1.89 pF and C_gd = 0.18 pF). Lower parasitic capacitances lead to a much higher cut-off frequency (f_t) of 46 GHz and a maximum oscillation frequency (f_max) of 130 GHz than those of the GFP structure (i.e., f_t = 27 GHz and f_max = 93 GHz). These results illustrate the superiority of the 2FFP structure for RF GaN HEMT and open up enormous opportunities for integrated RF GaN devices. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductor Materials, Devices and Systems)

► Show Figures

Figure 1

10 pages, 3266 KiB

Open AccessArticle

Numerical Modelling for the Experimental Improvement of Growth Uniformity in a Halide Vapor Phase Epitaxy Reactor for Manufacturing β-Ga₂O₃ Layers

by Galia Pozina, Chih-Wei Hsu, Natalia Abrikossova and Carl Hemmingsson

Crystals 2022, 12(12), 1790; https://doi.org/10.3390/cryst12121790 - 09 Dec 2022

Viewed by 1717

Abstract

The development of growth processes for the synthesis of high-quality epitaxial layers is one of the requirements for utilizing the ultrawide band gap semiconductor Ga₂O₃ for high-voltage, high-power electronics. A halide vapor phase epitaxy (HVPE) process used to grow β-Ga [...] Read more.

The development of growth processes for the synthesis of high-quality epitaxial layers is one of the requirements for utilizing the ultrawide band gap semiconductor Ga₂O₃ for high-voltage, high-power electronics. A halide vapor phase epitaxy (HVPE) process used to grow β-Ga₂O₃ layer was optimized by modifying the gas inlet, resulting in improved growth uniformity. A conventional tube acting as an inlet for the Ga precursor GaCl gas was replaced with a shower head with four outlets at 45 degrees to the horizontal axis of the reactor. The modification was performed based on numerical calculations of the three-dimensional distribution of gases inside the growth chamber with different designs of the GaCl precursor inlet. It was shown that variation in the Ga/O ratio over the substrate holder was ~10% for a shower head compared with ~40% for a tube. In addition, growth with a tube leads to the film thickness varying by a factor of ~4 depending on the position on the holder, whereas when using a shower head, the thickness of the grown Ga₂O₃ layers became much more uniform with a total spread of just ~30% over the entire substrate holder. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductor Materials, Devices and Systems)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Wide-Bandgap Semiconductor Materials, Devices and Systems

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (8 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI