Aluminum Nitride Research Articles

Thermal conductivity of epoxy resin films doped with a polythiophene/graphene complex or aluminum nitride

AbstractPolymer composites with thermal conductivity are attractive for heat dissipation in electronic devices. We prepared epoxy resin‐based composite films filled with polythiophene [poly(3‐hexylthiophene‐2,5‐diyl)] (P3HT)/graphene complex or aluminum nitride (AlN). The composite films were characterized by electron microscopic observation, thermogravimetric analysis, and thermal conductivity measurements. The addition of a small content of P3HT/graphene complex (<1 wt%) increased both the out‐of‐plane and in‐plane thermal conductivities of the epoxy resin. The addition of AlN also increased thermal conductivity, but ≥40 wt% was required to obtain thermal conductivity comparable with that of an epoxy resin film doped with 0.9 wt% P3HT/graphene complex. The present results illustrate the potential of P3HT/graphene complexes as fillers for improving the thermal conductivity of epoxy resins without affecting their insulating properties.Highlights Polythiophene/graphene fillers increased epoxy resin films' thermal conductivity. To raise the thermal conductivity of epoxy resin films high AlN content was needed. In‐plane/out‐of‐plane epoxy resin films' thermal conductivities were evaluated.

Synchrotron radiation x-ray topography applied to nitride semiconductor crystals

Gallium nitride (GaN) and aluminum nitride (AlN), as examples of third-generation semiconductors, have attracted significant interest due to their remarkable physical attributes, including a wide bandgap, high breakdown voltage, exceptional chemical stability, and high thermal conductivity. These characteristics render GaN and AlN highly promising for use in power and (opto)-electronic devices. Consequently, there is a growing demand for high-quality GaN and AlN crystals on the centimeter scale. As the dislocation density in these materials decreases, the need for a reliable method of dislocation characterization becomes more pressing. Synchrotron radiation x-ray topography (SR-XRT) has emerged as a superior, nondestructive technique for the precise characterization of crystal defects. This review briefly introduced the principle of XRT, and its application in the analysis of dislocations in GaN and AlN crystals is summarized. By examining the relationship between the SR-XRT image contrast and the Burgers vectors of dislocations, it is possible to categorize wafer dislocations and determine the magnitude and direction of Burgers vectors. Additionally, SR-XRT facilitates the analysis of interactions between dislocations in GaN and AlN crystals. These analyses are instrumental in advancing the development of superior crystals. This review concludes with a discussion of the current challenges faced by SR-XRT and a projection of its future applications in characterizing third-generation semiconductor crystal materials. This review offers significant guidance for the characterization of nitride crystal defects using SR-XRT.

Analysis of structural, electronic and optical properties of Er-doped rock salt AlN using ab-initio calculations.

This investigation includes the structural and optoelectronic characteristics of both pure and Er-doped rock salt aluminium nitride (AlN). Upon introducing Er doping into the AlN host, the calculations reveal a rise in the atomic parameter. Incorporating Er into the system leads to enhancements in the static dielectric coefficient ɛ1(0), static reflectivity R(0), as well as static refractive index n(0), at zero frequency. After doping, the peaks of imaginary dielectric tensor, extinction coefficient and absorption coefficient shift towards lower energy levels. Various exchange correlation potentials are incorporated to compare the results of electronic and optical characteristics. We employed the full potential linearized augmented plane wave (FP-LAPW) approach with WIEN2k code in conjunction with the density functional theory (DFT). To explore the optoelectronic characteristics of both pure as well as doped systems, three distinct exchange correlation potentials are utilized: the Perdew-Burke-Ernzerhof Generalized Gradient Approximation (PBE-GGA), Modified Becke Johnson Generalized Gradient Approximations (mBJ + GGA) and Hubbard potential (GGA + U).

An AlScN Piezoelectric Micromechanical Ultrasonic Transducer-Based Power-Harvesting Device for Wireless Power Transmission

Ultrasonic wireless power transfer technology (UWPT) represents a key technology employed for energizing implantable medical devices (IMDs). In recent years, aluminum nitride (AlN) has gained significant attention due to its biocompatibility and compatibility with complementary metal-oxide-semiconductor (CMOS) technology. In the meantime, the integration of scandium-doped aluminum nitride (Al90.4%Sc9.6%N) is an effective solution to address the sensitivity limitations of AlN material for both receiving and transmission capabilities. This study focuses on developing a miniaturized UWPT receiver device based on AlScN piezoelectric micro-electromechanical transducers (PMUTs). The proposed receiver features a PMUT array of 2.8 × 2.8 mm2 comprising 13 × 13 square elements. An acoustic matching gel is applied to address acoustic impedance mismatch when operating in liquid environments. Experimental evaluations in deionized water demonstrated that the power transfer efficiency (PTE) is up to 2.33%. The back-end signal processing circuitry includes voltage-doubling rectification, energy storage, and voltage regulation conversion sections, which effectively transform the generated AC signal into a stable 3.3 V DC voltage output and successfully light a commercial LED. This research extends the scope of wireless charging applications and paves the way for further device miniaturization by integrating all system components into a single chip in future implementations.

Toughness enhancement in TiN/Zr0.37Al0.63N1.09 multilayer films

The hardness and fracture toughness of high-temperature wear-resistant transition metal aluminum nitride multilayer films depend largely on the constituting layer's structure, compositional modulation, morphology, and interface coherency. We present a study on 1-micron thick multilayered films consisting of stacked layers of TiN and Zr0.37Al0.63N1.09, each layer being 10 nm thick. The films were grown using ion-assisted reactive magnetron sputtering on MgO(001) and Si(001) at substrate temperatures ranging from ambient to 900°C. By increasing growth temperature, we found that the ZrAlN layers transition from near amorphous to nanocrystalline wurtzite to decomposed c-ZrN and w-AlN domains. Concurrently, the TiN layers exhibit strong fiber texture, polycrystallinity, and epitaxial growth carried by the ZrN domains. Both hardness and fracture stress, evaluated by nanoindentation and micromechanical tests, increase with temperature from H=24 GPaMgO, 23 GPaSi to 36 GPaMgO, 30 GPaSi, and σFSi= 6.1-7.7 GPa, respectively. An improved fracture toughness of KIC=2.4-2.8 MPa√m is related to different toughening mechanisms for the various microstructures. The difference in hardness between the substrates is related to compressive stress due to the deposition conditions and thermal contraction. The superior fracture stress is attributed to dense multilayers, free from macroscopic defects due to ion-assisted growth. After being deposited at 200°C, the multilayers remained thermally stable when vacuum annealed for 15 hours at 900°C, with no significant change in phase composition or hardness. The improved hardness, toughness, and temperature stability of the otherwise brittle nitrides are promising for industrial applications.

Design and Fabrication of a Film Bulk Acoustic Wave Filter for 3.0 GHz-3.2 GHz S-Band.

Film bulk acoustic-wave resonators (FBARs) are widely utilized in the field of radio frequency (RF) filters due to their excellent performance, such as high operation frequency and high quality. In this paper, we present the design, fabrication, and characterization of an FBAR filter for the 3.0 GHz-3.2 GHz S-band. Using a scandium-doped aluminum nitride (Sc0.2Al0.8N) film, the filter is designed through a combined acoustic-electromagnetic simulation method, and the FBAR and filter are fabricated using an eight-step lithographic process. The measured FBAR presents an effective electromechanical coupling coefficient (keff2) value up to 13.3%, and the measured filter demonstrates a -3 dB bandwidth of 115 MHz (from 3.013 GHz to 3.128 GHz), a low insertion loss of -2.4 dB, and good out-of-band rejection of -30 dB. The measured 1 dB compression point of the fabricated filter is 30.5 dBm, and the first series resonator burns out first as the input power increases. This work paves the way for research on high-power RF filters in mobile communication.

Highly Wavelength-Selective Self-Powered Solar-Blind Ultraviolet Photodetector Based on Colloidal Aluminum Nitride Quantum Dots.

Colloidal quantum dots are semiconductor nanocrystals endowed with unique optoelectronic properties. A major challenge to the field is the lack of methods for synthesizing quantum dots exhibit strong photo-response in the deep-ultraviolet (DUV) band. Here, a facile solution-processed method is presented for synthesizing ultrawide bandgap aluminium nitride quantum dots (AlN QDs) showing distinguished UV-B photoluminescence. Combined with the strong optical response in solar blind band, a solution-processed, self-powered AlN-QDs/β-Ga2O3 solar-blind photodetector is demonstrated. The photodetector is characterized with a high responsivity of 1.6mAW-1 under 0V bias and specific detectivity 7.60 × 10-11 Jones under 5V bias voltage with good solar blind selectivity. Given the solution-processed capability of the devices and extraordinary properties of AlN QDs, this study anticipates the utilization of AlN QDs will open up unique opportunities for cost-effective industrial production of high-performance DUV optoelectronics for large-scale applications.

Analysis of lattice deformation originated from residual stress on performance of aluminum nitride-based bulk acoustic wave resonators

With the development of MEMS technology to the nanometer scale, the influence of different process conditions on the performance of nano-devices can be calculated through the microscopic changes of materials. During the manufacturing process, the large residual stress from the film stack significantly influences the performance of devices, thereby reducing the wafer yield. Herein, we apply density functional theory to MEMS processes to reveal the intrinsic mechanism of how residual stress affects the performance of aluminum nitride-based bulk acoustic wave (BAW) resonators on an 8-inch high-resistance silicon wafer. The variation rule of physical properties of piezoelectric material aluminum nitride with different residual stresses is calculated via first-principles calculations. Through theory formula derivation, the piezoelectric-coupling constant (Kt2) of the bulk acoustic wave resonator is positively correlated with tensile residual stress, and the resonant frequency (fp, fs) is negatively correlated with tensile residual stress. The measurement results show that the average shifts of Keff2 is 0.12 % within −137 MPa and 183 Mpa residual stress, which is an excellent match with the theory prediction.

DFT Studies on Structural, Electronic and Optical Properties of Aluminum Nitride Nanotube Doped by Different Concentrations of Boron

Nanotubes are an exceptional class of materials whose unusual properties depend on geometry and composition. In this work, we have investigated the optoelectronic properties of aluminum nitride nanotube doped with boron in concentrations of 4.2%, 8.3%, and 12.5% respectively. Analysis was done by considering the structural, electronic, and optical properties of the considered nanotubes using density functional theory implemented in quantum ESPRESSO and Yambo codes. Simulations revealed that doped aluminum nitride nanotube whose nitrogen atoms were replaced turned to metallic while doped aluminum nitride nanotube whose aluminum atoms were replaced retained its semiconducting characteristics showing various band gaps with different concentrations of dopants. Optical absorption behaviors revealed that 8.3% B-doped aluminum nitride nanotube made better utilization of visible light than others and hence can be used as a candidate for dye degradation and wastewater treatment, solar cell, LED, and LASER. In the end, all the doped nanotubes were found to be worthy for various fields of science and technology.

Preparation and properties of a new high-energy metal (W) film/aluminum nitride system energy exchanger electrothermal pyrogenant

In order to improve the safety and energy exchange efficiency of electric thermal pyrotechnic devices, a new energy exchange element technology of high energy metal (W) film/aluminum nitride ceramic was explored by taking advantage of the high thermal conductivity of aluminum nitride ceramic materials. High-temperature co-fired ceramics were used to prepare the new system energy exchangers, and the prototype of the new system energy exchanger of high-energy metal (W) film/aluminum nitride was obtained. Through infrared microscopic test and ignition performance test, the new system energy exchanger of high-energy metal (W) film/aluminum nitride can satisfy the 1A1W5min non-ignition test, and the ignition current of 50% is 2.80 A. The response current of 99.9% is 3.54 A, and the response current of 0.1% is 2.06 A, which provides technical support for the application of a new type of passivated electric thermal pyrogenic product.

Assessing the gas sensing capability of undoped and doped aluminum nitride nanotubes.

CO2 and CO gas sensors are very important to recognize the insulation situation of electrical tools. ToCO explore the application of noble metal doped of aluminum nitride nanotubes for gas sensors, DFT computations according to the first principal theory were applied to study sensitivity, adsorption attributes, and electronic manner. In this investigation, platinum-doped aluminum nitride nanotubes were offered for the first time to analyze the adsorption towards CO2 and CO gases. Firm construction of platinum-doped aluminum nitride nanotubes (Pt-AlNNT) was investigated in four feasible places, and the binding energy of firm construction is 1.314 eV. Respectively, the adsorption energy between the CO2 and Pt-AlNNT systems was - 2.107 eV, while for instance of CO, the adsorption energy was - 3.258 eV. The mentioned analysis and computations are considerable for studying Pt-AlNNT as a new CO2 and CO gas sensor for electrical tools insulation. The current study revealed that the Pt-AlNNT possesses high selectivity and sensitivity towards CO2 and CO. In this research, Pt-doped AlNNT (Pt-AlNNT) has been studied as sensing materials of CO and CO2 for the first time. The adsorption process of Pt-AlNNT has been computed and analyzed through the DFT approach. DFT computations by using B3LYP functional and 6-31 + G* basis sets have been applied in the GAMESS code for sensing attributes, which contribute to potential applications.

Aluminum Nitride MEMS Resonant Pressure Gauges Without Vacuum Packaging

Aluminum Nitride MEMS Resonant Pressure Gauges Without Vacuum Packaging

Orbital hybridization and defective states of vacancy defects in AlN

Intrinsic atomic defects pose a great effect in wide-bandgap semiconductors owing to the high tendency of forming in-gap defective states. Utilizing density-functional theory, the atomic vacancy defects of Al and N vacancies in hexagonal wurtzite aluminum nitride (AlN) are investigated. We find that the most energetically favorable form of vacancies is predicted to be negatively trivalent charged Al vacancy (VAl−3) in n-type AlN and positively monovalent charged N vacancy (VN+1) in p-type AlN, respectively. N vacancy generally has a low formation energy and could be either an acceptor or a donor: Under p-type conduction, it is a deep donor with a positively monovalent charge of +1, acting as a compensating center for holes; Under n-type conduction, it is a deep acceptor carrying charge of −3, acting as a compensating center for electrons. For the Al vacancy, it tends to be a shallow acceptor in p-type AlN but a high formation energy or a deep acceptor in n-type AlN with low formation energy, most possibly at a negatively trivalent charged state. Our orbital hybridization analysis shows that these vacancies can be facilely generated which are rooted in the antibonding coupling Al3 s-N2p states in valence band. The above finding is independent of the chemical potential of nitrogen and aluminum and holds true under both nitrogen rich and poor conditions. Our work provides a guide to experimental works by providing the energetics and atomic-scale mechanism of doping nature of atomic vacancies in AlN.

Comparison of aluminum nitride thin films prepared by magnetron sputter epitaxy in nitrogen and ammonia atmosphere

Wurtzite-type aluminum nitride (AlN) thin films exhibiting high thermal conductivity, large grain size, and low surface roughness are desired for both bulk acoustic wave and surface acoustic wave resonators. In this work, we use ammonia (NH3) assisted reactive sputter deposition of AlN to significantly improve these properties. The study shows a systematic change in the structural, thermal, and morphological properties of AlN grown in nitrogen (N2) and N2 + NH3 atmosphere. The study demonstrates that NH3 assisted AlN sputtering facilitates 2D growth. In addition, the study presents a growth model relating the 2D growth to improve the mobility of aluminum (Al) and nitrogen (N) ad-atoms in NH3 atmosphere. Consequently, the thermal conductivity and roughness improve by ≈76%, and ≈35%, while the grain size increases by ≈78%.

Demonstration of 4H silicon carbide on aluminum nitride integrated photonics platform

Demonstration of 4H silicon carbide on aluminum nitride integrated photonics platform

Diffusion Nitride Surface Layers on Aluminum Substrates Produced by Hybrid Method Using Gas Nitriding

Diffusion Nitride Surface Layers on Aluminum Substrates Produced by Hybrid Method Using Gas Nitriding

The effect of friction stir processing on mechanical, wear and corrosion characteristics of Cu-AlN-BN surface composite

This research investigates the impact of hybrid particles dispersed onto the surface of a copper matrix using Friction Stir Processing (FSP) on its microstructural, mechanical, and corrosion behavior. The hybrid particles under study consist of equal fractions of Aluminium Nitride (AlN) and Boron Nitride (BN). Microstructural characterization confirms breakdown of grain size due to dynamic recrystallization and presence of particles, along with their effective bonding to copper matrix. Attained results indicated a significant enhancement in hardness, with an increase of up to 3.9 % upon the introduction of particles onto the surface. Moreover, the tensile properties exhibit noticeable improvements in terms of ultimate tensile strength (6.39 %) and yield strength (6.12 %), albeit at the expense of reduced ductility in the copper matrix. Furthermore, the wear rate (decreases up to 22 %) and corrosion rate of the developed composites demonstrate a decreasing trend with the introduction of particles. This improvement can be attributed to the reduction in grain size during the FSP process and the formation of a nitride passive layer facilitated by the reinforced hybrid particles, thereby effectively inhibiting the corrosion rate.

Systematic improvements in transmon qubit coherence enabled by niobium surface encapsulation

We present a transmon qubit fabrication technique that yields systematic improvements in T1 relaxation times. We encapsulate the surface of niobium and prevent the formation of its lossy surface oxide. By maintaining the same superconducting metal and only varying the surface, this comparative investigation examining different capping materials, such as tantalum, aluminum, titanium nitride, and gold, as well as substrates across different qubit foundries demonstrates the detrimental impact that niobium oxides have on coherence times of superconducting qubits, compared to native oxides of tantalum, aluminum or titanium nitride. Our surface-encapsulated niobium qubit devices exhibit T1 relaxation times 2–5 times longer than baseline qubit devices with native niobium oxides. When capping niobium with tantalum, we obtain median qubit lifetimes above 300 μs, with maximum values up to 600 μs. Our comparative structural and chemical analysis provides insight into why amorphous niobium oxides may induce higher losses compared to other amorphous oxides.

Fabrication of High Thermal Conductivity Aluminum Nitride Ceramics via Digital Light Processing 3D Printing.

The sintering of high-performance ceramics with complex shapes at low temperatures has a significant impact on the future application of ceramics. A joint process of digital light processing (DLP) 3D printing technology and a nitrogen-gas pressure-assisted sintering method were proposed to fabricate AlN ceramics in the present work. Printing parameters, including exposure energy and time, were optimized for the shaping of green bodies. The effects of sintering temperature, as well as nitrogen pressure, on the microstructure, density, and thermal conductivity of AlN ceramics were systematically discussed. A high thermal conductivity of 168 W·m-1·K-1 was achieved by sintering and holding at a significantly reduced temperature of 1720 °C with the assistance of a 0.6 MPa nitrogen-gas pressure. Further, a large-sized AlN ceramic plate and a heat sink with an internal mini-channel structure were designed and successfully fabricated by using the optimized printing and sintering parameters proposed in this study. The heat transfer performance of the ceramic heat sink was evaluated by infrared thermal imaging, showing excellent cooling abilities, which provides new opportunities for the development of ceramic heat dissipation modules with complex geometries and superior thermal management properties.

Doubly resonant metal-free electro-optic microwave receiver in aluminum nitride

Doubly resonant metal-free electro-optic microwave receiver in aluminum nitride