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Based on metal organic chemical vapor deposition (MOCVD), growth mechanism and stress modulation of van der Waals (vdW) heteroepitaxial GaN microwave material were studied with few-layer BN as an interlayer on 4-inch sapphire substrates. The influence of AlN nucleate process on growth mechanism of GaN buffer layer and its correlation with crystalline quality, stress, and electrical properties were discussed. A stress modulation scheme based on AlN/ AlGaN composite nucleation process is proposed, achieving stress well in control for large-size vdW heteroepitaxy firstly. The as-grown GaN microwave material possesses a wafer bow of + 20. 4 μm, fullwidth at half maximum of GaN (002) / (102) peaks of 471. 6/933. 5 arcsec, root-mean-square roughness of 0. 52 nm and electron mobility of 2 000 cm² / (V·s). Finally, largesize wafe-scale GaN microwave material was successfully separated from sapphire substrate by a mechanical lift-off process, providing convenience for transfering to high thermal conductivity substrates and creating conditions for fabricating high-power RF devices. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian University of Technology / Dalian Ligong Daxue Xuebao is the property of Journal of Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The electrode made of transparent semiconductor indium tin oxide (ITO) can reduce the edge current crowding effect of photoconductive semiconductor switches and improve the utilization of pulse laser. In this paper, 10 nm Ti and TiN layer were inserted into the interface between ITO and GaN, and the influences of Ti and TiN layer on the Ohmic contact performance between ITO and GaN were studied. I-V test results show that with the increase of the annealing temperature, the GaN photoconductive semiconductor switch with Ti insertion layer changes from Ohmic contact to Schottky contact, while the photoconductive semiconductor switch with TiN insertion layer keeps Ohmic contact characteristics. TEM observation shows that when Ti is used as the insertion layer, ITO diffuses through the insertion layer to the interface between the insertion layer and GaN, resulting in the formation of Ti oxide and holes at the interface. The transmission spectra show that the transmittance of samples with Ti insertion layer is less than 38.3% at different annealing temperatures, while the transmittance is 38.8% ~55.0% when TiN is used as the insertion layer. Therefore, the photoconductive semiconductor switch containing TiN insertion layer shows a higher thermal stability and transmittance, which provides reference for the application of GaN photoconductive semiconductor switch in the field of high temperature and high power. [ABSTRACT FROM AUTHOR]

Solid-state power amplifiers using semiconductor technology have the advantages of small size and high stability, and have replaced traditional travelling wave tube amplifiers in many microwave applications. Among all types of semiconductor materials, the third-generation semiconductor material GaN(Gallium Nitride) has been widely used in power amplifiers because of its advantages of wide band gap, high electron mobility, and high breakdown voltage. Based on the development of power amplifiers, this study describes the development history of solid-state power amplifiers, summarizes the performance comparison between GaN technology and other semiconductor technologies, and focuses on power amplifiers using GaN HEMT(GaN High Electron Mobility Transistor) technology. This study discusses various types of GaN HEMT power amplifiers, including class A, B, C, D, and E, etc., introduces the efficiency and linearity improvement techniques applied to GaN power amplifiers, including Doherty power amplifiers and envelopes tracking technology, and digital pre-distortion technology, etc., and makes a summary and comparison of related technologies. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Beijing University of Technology is the property of Journal of Beijing University of Technology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the widespread application of gallium nitride (GaN) in the high-power field, the heat dissipation of GaN based devices has become the main factor restricting the power density. Therefore, it is crucial to develop novel thermal management solutions. Diamond substrates with high thermal conductivity can be used to improve the heat dissipation of GaN devices. However, due to the natural lattice mismatch between diamond and GaN, the direct epitaxy of GaN on diamond substrates remains an insurmountable problem. This work achieved van der Waals epitaxy of single crystal GaN films on polycrystalline diamond substrates using a two-dimensional material / Al gradient AlGaN heterostructure as the nucleation layer between the substrate and the epitaxial layer. Among them, two-dimensional materials can effectively shield against the adverse effects caused by lattice mismatch between the substrate and epitaxial layer, while the Al component gradient AlGaN buffer layer can achieve orderly migration of Ga and N atoms, thereby accurately controlling the growth of GaN thin films. This work provides a novel approach for high-quality growth of nitrides on heterogeneous substrates. The experimental results indicate that the introduction of nucleation layers effectively eliminates the impact of lattice mismatch, thereby breaking the bottleneck of the difficulty in directly epitaxial single crystal GaN films on diamond substrates. This work provides a foundation for further improving the power density of GaN based devices. [ABSTRACT FROM AUTHOR]

In this study, a large area laser lift-off (LLO) of GaN-based micro light-emitting diodes (Micro LED) was achieved using an excimer laser at 248 nm. The critical laser energy density required for separation of devices is 800 ~ 835 mJ·cm - 2. The separated device is intact with a residual stress of 0. 071 4 GPa and a mean square roughness of 0. 597 nm, which is much lower than that of the LLO method reported so far. This study provides a promising idea for the fabrication of GaN-based Micro LED chips with high quality and high efficiency, which is of great significance for the fabrication of flexible GaN-based devices. [ABSTRACT FROM AUTHOR]

A novel coupled barrier heterojunction structure ( i. e. Al 0. 26 Ga0. 74 N/ GaN/ Al 0. 20 Ga0. 80 N/ GaN) was proposed and prepared in this paper to improve transconductance linearity of GaN high electron mobility transistor. A double two-dimensional electron gas (2DEG) channel in the coupled barrier heterojunction structure is demonstrated by theoretically calculation and capacitance-voltage (C-V) measurement. 2DEG mobility of 1 510 cm 2·V - 1·s - 1 and sheet density of 9. 7 × 10 12 cm - 2 are obtained. Benefiting from the double channels, the transconductance profile of the device with coupled heterojunction barrier structure shows two peaks, and the voltage swing is 3. 0 V, which is 1. 5 times larger than that of normal structure. First-order and second-order derivative characteristics of transconductance indicate that the device of the coupled barrier structure has higher harmonic suppression capability. This study demonstrates a superiority of coupled barrier heterojunction in the area of high linearity application. [ABSTRACT FROM AUTHOR]

Due to the advantages of both large size, low cost, and compatibility with existing CMOS processes, GaN based ratio frequency (RF) electronic materials and devices on Si substrates have become the next focus of attention in this field after power electronic devices. Due to the different mechanical properties of high-resistivity Si substrates, it is still difficult to control stress and suppress dislocations in the growth of GaN based epitaxial materials on high-resistivity Si substrates, as well as address serious RF loss issues that limit their applications in the field of RF electronics. This work briefly introduces the research status and challenges of GaN based RF electronic materials on Si substrates, focusing on the main research progress of the Peking University research team in the formation mechanism of RF loss, epitaxial growth of GaN on high-resistivity Si substrates with low dislocation density and low RF loss. Finally, the future development of GaN based RF electronic materials and devices on Si substrates is prospected. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Gallium nitride (GaN) material has become a research hotspot at home and abroad because of its unique properties and application prospects. High quality GaN single crystals are the prerequisite for obtaining optoelectronic devices and power devices with excellent performance. Because of its mild growth conditions, the sodium flux method is easy to obtain high quality and large size GaN single crystals, and it is a promising method for the growth of GaN single crystals. Since the sodium flux method was invented in the late 1990s, the crystals grown by the sodium flux method have made considerable progress in size and quality after more than 20 years of development. Recent research progress of GaN single crystals grown by the sodium flux method from the aspects of crystal growth principle, seed crystal selection, temperature gradient and additives are summarized in this paper, and the challenges and future development trend are also prospected. [ABSTRACT FROM AUTHOR]

Copyright of Electric Drive is the property of Electric Drive Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The substitution position of indium (In) atoms is significant for developing novel orthorhombic GaN hydrogen storage materials. Currently, research on the influence of In atom substitution position on the orthorhombic GaN is still relatively limited. In this paper, based on the first-principles, formation energy, electronic structure, elastic properties, and mechanical stability of InGaN materials with different In atom substitution positions were studied. The results show that the formation energy of In atom substitution position separated by three atoms is the smallest, and the structure is most easily formed. Under the same doping conditions, the InGaN materials with this structure also have larger band gap and smaller elastic modulus, bulk modulus, shear modulus, and elasticity modulus, which means that its compressive strength and shear stress are slightly weaker, and its toughness and hardness are lower. In addition, the calculation results of phonon spectrum show that the InGaN material with three atoms interval also has good mechanical stability under ambient pressure. This study provides a theoretical basis for studying new hydrogen storage metamaterials with orthorhombic GaN. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Guangdong University of Technology is the property of Journal of Guangdong University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the polarization luminescence characteristics of the near-band-edge peak and Fe3 + related emission peaks(4T1 (G)-6A1 (S)) of the non-polar surfaces including a-plane {11 20} and m-plane {1 100} of Fe-doped GaN crystal were studied by low-temperature photoluminescence(PL) measurement. The results show that the optical anisotropy of a-plane and m-plane are similar. When the linearly polarized electric-field vector E is parallel to the c-direction [0001] (E//c), the intensity of GaN near-band-edge peak is the lowest, and the intensity of Fe3+ zero-phonon line (1.299 eV) is the strongest. The degree of polarization of Fe3+ zero-phonon line is greater than that of near-band-edge peak. The degree of polarization of near-band-edge peak of a-plane is 26%, while the degree of polarization of Fe3+ zero-phonon line reaches up to 55% and 58% of a-plane and m-plane GaN, respectively. The polarization characteristics of Fe3+ fine peak and the additional lines are further measured at 5 K. The results show that, except for one weak peak, other peaks are consistent with the polarization characteristics of Fe3+ zero-phonon line. This study is helpful to expand the application of Fe-doped GaN crystal in the field of novel optical and electrical devices. [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN) high electron mobility transistor (HEMT) has attracted much attention due to its high breakdown field strength, low on-resistance and high conversion efficiency, and it is expected to be applied in power electronics systems. However, its high power density and high frequency characteristics bring great challenges to packaging technology. The parasitic inductance parameters in the package of traditional silicon power electronic devices is large, which will cause switch oscillation and other problems, so that the excellent performance of GaN cannot be fully utilized. In addition, the thermal management ability of the package determines the reliability of the power device. If the self-heating effect of the device cannot be well solved, its performance will be reduced, and even the chip will be burned. On the basis of explaining the switching oscillation and thermal management problems caused by traditional packaging technology applied to gallium nitride power electronic devices, the research progress of GaN packaging technology aiming at the above problems are reviewed in detail in this paper, including by optimizing the control circuit, reducing Lg inductancing, improving Rg inhibition of dv/dt, increasing ferrite beads on the gate electrode, PCB layout optimization and increasing magnetic flux offset method to solve the problem of switch oscillation caused by the parasitic inductance, the application of high thermal conductivity material of diamond in devices thermal management, improvement of device package structure and other heat dissipation technologies. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Posts & Telecommunications (Natural Science Edition) is the property of Chongqing University of Posts & Telecommunications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Zhengzhou University (Natural Science Edition) is the property of Journal of Zhengzhou University (Natural Science Edition) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Tiangong University is the property of Journal of Tianjin Polytechnic University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Electroplating & Finishing is the property of Electroplating & Finishing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)