Gallium Nitride Heterostructures Research Articles

Heterogeneous integration of high-k complex-oxide gate dielectrics on wide band-gap high-electron-mobility transistors

Heterogeneous integration of dissimilar crystalline materials has recently attracted considerable attention due to its potential for high-performance multifunctional electronic and photonic devices. The conventional method for fabricating heterostructures is by heteroepitaxy, in which epitaxy is performed on crystallographically different materials. However, epitaxial limitations in monolithic growth of dissimilar materials prevent implementation of high quality heterostructures, such as complex-oxides on conventional semiconductor platforms (Si, III-V and III-N). In this work, we demonstrate gallium nitride (GaN) high-electron-mobility transistors with crystalline complex-oxide material enabled by heterogeneous integration through epitaxial lift-off and direct stacking. We successfully integrate high-κ complex-oxide SrTiO3 in freestanding membrane form with GaN heterostructure via a simple transfer process as the gate oxide. The fabricated device shows steep subthreshold swing close to the Boltzmann limit, along with negligible hysteresis and low dynamic on-resistance, indicating very low defect density between the SrTiO3 gate oxide and GaN heterostructure. Our results show that heterogeneous integration through direct material stacking is a promising route towards fabricating functional heterostructures not possible by conventional epitaxy.

Interfacial thermal conductance of gallium nitride/graphene/diamond heterostructure based on molecular dynamics simulation

Gallium Nitride chips are widely used in high-frequency and high-power devices. However, Thermal management is a critical challenge for gallium nitride devices.To improve thermal dissipation of gallium nitride devices, the Nonequilibrium Molecular Dynamics method was employed to investigate the effects of operating temperature, interface size, defect density and defect types on the interfacial thermal conductance of gallium nitride/graphene/diamond heterostructure. Furthermore, the phonon state density and phonon participation ratio under various conditions were calculated to analyze the interface thermal conduction mechanism. The results indicate that interfacial thermal conductance increases with rising temperatures, highlighting the inherent self-regulating heat dissipation capabilities of heterogeneous. The interfacial thermal conductance of monolayer graphene structures increases by 2.1 times as the temperature increases from 100 K to 500 K. This is attributed to the overlap factor increases with temperature, which enhanced the phonon coupling between interfaces, leading to an increase in interfacial thermal conductance. Additionally, The study discovered that both increasing the number of layers of gallium nitride and graphene leads to reduction in interfacial thermal conductance.When the number of gallium nitride layers increases from 10 to 26, the interfacial thermal conductance decreases by 75%. The diminishing overlap factor with the increase in layer number is attributed to the decreased match of phonon vibrations between interfaces, resulting in lower thermal transfer efficiency. Similarly, when the number of graphene layers increases from 1 to 5, the interfacial thermal conductance decreases by 74%. The increase in graphene layers leads to reduction in low-frequency phonons, consequently lowering the interfacial thermal conductance. Moreover, multilayer graphene intensifies phonon localization, exacerbating the reduction in interfacial thermal conductance. The introduction of four types of vacancy defects is found to influence interfacial thermal conductance. Diamond carbon atom defects lead to increase in interfacial thermal conductance, whereas defects in gallium, nitrogen, and graphene carbon atoms result in decrease. As the defect concentration increases from 0 to 10%, Diamond carbon atom defects increased the interfacial thermal conductance by 40% due to defect scattering, which increased the number of low-frequency phonon modes and expanding the channels for interfacial heat transfer, thus ameliorating interfacial thermal conductance. Defects in graphene intensify the degree of graphene phonon localization, consequently leading to reduction in interfacial thermal conductance. Gallium and nitrogen defects both intensify the phonon localization of gallium nitride, impeding phonon transport channels. Moreover, gallium defects induce more severe phonon localization compared to nitrogen, consequently leading to lower interfacial thermal conductance. This research provides references for the manufacturing of highly reliable gallium nitride devices and the widespread use of gallium nitride heterostructures.</p>

A Closed-Form Model for 2-DEG Charge and Surface Potential in N-Polar Gallium Nitride Heterostructures

A closed-form model to calculate the 2-D electron gas (2-DEG) charge density and surface potential in an N-polar GaN/AlGaN heterostructure is presented. The proposed model is developed from the solution of Schrödinger’s equation for a finite triangular potential well. Asymptotic expressions of Airy functions are used to compute an initial value of subband energy. A new, unified expression to update the surface potential due to Poisson’s equation is presented. The modified Fang–Howard (M.F.H.) function is then employed to develop a closed-form correction to the subband energy using first-order perturbation theory. No fitting parameters are used. The results from our model are validated with numerical data for a wide range of bias conditions, channel layer thickness, and spacer layer mole fraction. Finally, the gate capacitance of the heterostructure is evaluated using automatic differentiation and validated against experimental data.

Transistors with High Electron Mobility Based on Gallium-Nitride Heterostructures for Millimeter Wavelengths

Transistors with High Electron Mobility Based on Gallium-Nitride Heterostructures for Millimeter Wavelengths

Airy Function-Based Model for 2-DEG Charge and Surface Potential in N-Polar Gallium Nitride Heterostructures

A systematic, analytical method to obtain the charge density and surface potential in an N-polar GaN/AlGaN heterostructure is presented. This method also provides the wave functions, subband energies, and band diagram. The model accounts for the greater leakage of the wave functions into the spacer and barrier layers in the N-polar structure as compared to the Ga-polar structure. The framework is based on the solution of Schrödinger–Poisson equations for an approximately triangular well potential with finite confinement, achieved using first-order perturbation theory. No fitting parameters are used. Results obtained using our model are in good agreement with numerical results (obtained using the finite difference method) for a wide range of bias conditions (from OFF- to ON-states) and Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> Ga <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{1}-{x}}\text{N}$ </tex-math></inline-formula> spacer mole fractions.

Large Signal Performance of the Gallium Nitride Heterostructure Field-Effect Transistor With a Graphene Heat-Removal System

The self-heating effect exerts a considerable influence on the characteristics of high-power electronic and optoelectronic devices based on gallium nitride. An extremely non-uniform distribution of the dissipated power and a rise in the average temperature in the gallium nitride heterostructure field-effect transistor lead to the formation of a hot spot near the conductive channel and result in the degradation of the drain current, power gain and device reliability. The purpose of this work is to design a gallium nitride heterostructure field-effect transistor with an effective graphene heat-removal system and to study using numerical simulation the thermal phenomena specific to it. The object of the research is the device structure formed on sapphire with a grapheme heat-spreading element placed on its top surface and a trench in the passivation layer filled with diamond grown by chemical vapor deposition. The subject of the research is the large signal performance quantities. The simulation results confirm the effectiveness of the heat-removal system integrated into the heterostructure field-effect transistor and leading to the suppression of the self-heating effect and to the improvement of the device performance. The advantage of our concept is that the heat-spreading element is structurally connected with a heat sink and is designed to remove the heat immediately from the maximum temperature area through the trench in which a high thermal conductivity material is deposited. The results of this work can be used by the electronics industry of the Republic of Belarus for developing the hardware components of gallium nitride power electronics.

Development of Monolithic Integrated Circuits on Gallium Nitride Heterostructures

The article describes IUHFSE RAS experience in designing MMICs based on gallium nitride heterostructures on various types of substrates: sapphire, silicon and silicon carbide in the frequency range from 10 GHz to 96 GHz. Such as power amplifiers, low-noise amplifiers, and a chipset for radio communications and radiolocation: voltage-controlled oscillators, mixers, multi¬pliers, and transceiver MMIC with integrated antennas. HEMT transistors based on gallium nitride are a suitable for creating a radiation resistant components for frequencies up to 100 GHz.

MoSe2/n‐GaN Heterojunction Induced High Photoconductive Gain for Low‐Noise Broadband Photodetection from Ultraviolet to Near‐Infrared Wavelengths

AbstractHeterojunction photodiodes comprising of layered metal chalcogenides and wide‐bandgap semiconductors are a promising candidate for broadband photodetection. In this work, nanolayered Molybdenum diselenide (MoSe2)/Gallium Nitride (GaN) based photodetector has been demonstrated from ultraviolet to near‐infrared range (300–1000 nm). The performance is investigated by conducting Kelvin probe force microscopy to measure the conduction band offset at the interface of the heterojunction. It is used to analyze the energy‐band diagrams to understand the current transport mechanism. The device exhibits a high photoconductive gain of 1.8 × 104, responsivity of 5580 A W−1, detectivity of 1.9 × 1011 Jones and low noise equivalent power of 10 fW Hz−1/2 at 365 nm. Additionally, finite difference time domain simulations are performed for the MoSe2/n‐GaN heterostructure to authenticate the broadband photodetection spectrum. Therefore, the outcomes of this study validate the suitability of MoSe2/n‐GaN heterojunction devices for high responsivity and detectivity applications.

Gallium nitride heterostructure field-effect transistor with a heat-removal system based on a trench in the passivation layer filled by a high thermal conductivity material

The self-heating effect poses a main problem for high-power electronic and optoelectronic devices based on gallium nitride. A non-uniform distribution of the dissipated power and a rise of the average temperature inside the gallium nitride heterostructure field-effect transistor lead to the formation of a hot spot near the conducting channel and result in the degradation of the drain current, output power and device reliability. The purpose of this work is to develop the design of a gallium nitride heterostructure field-effect transistor with an effective heat-removal system and to study using numerical simulation the thermal phenomena specific to this device. The objects of the research are the device structures formed on sapphire, each of whom features both a graphene heat-eliminating element on its top surface and a trench in the passivation layer filled by a high thermal conductivity material. The subject of the research is the electrical and thermal characteristics of these device structures. The simulation results verify the effectiveness of the integration of the heat-removal system into the gallium nitride heterostructure field-effect transistor that can mitigate the self-heating effect and improve the device performance. The advantage of our concept is that the graphene heat-eliminating element is structurally connected with a heat sink and is designed for removing the heat immediately from the maximum temperature area through the trench in which a high thermal conductivity material is deposited. The results can be used by the electronics industry of the Republic of Belarus for developing the hardware components of gallium nitride power electronics.

Особенности роста гетероструктур нитрида галлия на подложках кремния: управляемая пластическая деформация

Gallium nitride heterostructures were grown on silicon substrates by metalorganic chemical vapour deposition. Substrate plastic deformations that occur during the growth process with the effective compressive stresses accumulation in the film were observed at temperatures of 930oC-975oC. An approach of silicon controlled plastic deformation by high-temperature annealing combined with the in situ SiNx layer growth after heterostructure epitaxy is proposed. This approach would simplify optimization of the gallium nitride heterostructures architecture for various technological tasks.

(Invited) GaN Optoelectronic Devices Based on Local Strain Engineering

Local strain engineering and its applications to gallium nitride based optoelectronic devices are reviewed. The strain in gallium nitride heterostructures can be locally controlled via nanostructures and enables a new degree of freedom for the device design. The optical properties including emission wavelength, intensity, polarization can be geometrically tuned by varying the dimensions and shapes of the nanostructure cross sections. The physics, fabrication, optical properties, and challenges of gallium nitride nanostructures are discussed. Device applications are described including single photon sources, multi-wavelength light-emitting diodes, photodetectors for compressive sensing, and tactile sensors.

Powerful Gallium Nitride Microwave Transistors on Silicon Substrates

Gallium nitride heterostructures on silicon substrates were grown by the method of gas-phase epitaxy from organometallic compounds. Based on them, transistors with a total gate width of 7.92 mm were created. The influence of the architecture of buffer layers on the characteristics of heterostructures and test transistors based on them is studied. Powerful transistors were obtained with an output pulse power of 45 W at a frequency of 1 GHz with a supply voltage of 28 V. The maximum efficiency of the transistor was 55%.

Physical-Based Simulation of the GaN-Based Grooved-Anode Planar Gunn Diode.

In this paper, a novel gallium nitride (GaN)-based heterostructure Gunn diode is proposed for the first time to enhance the output characteristics of Gunn oscillation waveforms. A well-designed grooved anode contact is adopted to separate the long-channel diode into two short-channel diodes in parallel. If the grooved anode contact is positioned in the middle of the device, the output power nearly doubles in the grooved-anode diode compared with the single-channel ones, as does the output frequency. Based on the numerical results, the best output characteristics are obtained at the 2.0-µm symmetrical grooved-anode diode, which produces nearly 5.48 mW of power at the fundamental frequency of 172.81 GHz, with 3.13% efficiency of power conversion. If the grooved anode contact is not positioned in the middle of the diode, the harmonic frequency would be enhanced. The GaN heterostructure grooved-anode Gunn diode has been demonstrated to be an excellent solid-state source of terahertz oscillator.

Absorption and emission modulation in a MoS2–GaN (0001) heterostructure by interface phonon–exciton coupling

Semiconductor heterostructures based on layered two-dimensional transition metal dichalcogenides (TMDs) interfaced to gallium nitride (GaN) are excellent material systems to realize broadband light absorbers and emitters due to their close proximity in the lattice constants. The surface properties of a polar semiconductor such as GaN are dominated by interface phonons, and thus the optical properties of the vertical heterostructure are influenced by the coupling of these carriers with phonons. The activation of different Raman modes in the heterostructure caused by the coupling between interfacial phonons and optically generated carriers in a monolayer MoS2–GaN (0001) heterostructure is observed. Different excitonic states in MoS2 are close to the interband energy state of intraband defect state of GaN. Density functional theory (DFT) calculations are performed to determine the band alignment of the interface and revealed a type-I heterostructure. The close proximity of the energy levels and the excitonic states in the semiconductors and the coupling of the electronic states with phonons result in the modification of carrier relaxation rates. Modulation of the excitonic absorption states in MoS2 is measured by transient optical pump-probe spectroscopy and the change in emission properties of both semiconductors is measured by steady-state photoluminescence (PL) emission spectroscopy. There is significant red-shift of the C excitonic band and faster dephasing of carriers in MoS2. However, optical excitation at energy higher than the bandgap of both semiconductors slows down the dephasing of carriers and energy exchange at the interface. Enhanced and blue-shifted PL emission is observed in MoS2. GaN band-edge emission is reduced in intensity at room temperature due to increased phonon-induced scattering of carriers in the GaN layer. Our results demonstrate the relevance of interface coupling between the semiconductors for the development of optical and electronic applications.

Intersubband Device Modeling of Gallium Nitride High Electron Mobility Transistor for Terahertz Applications

AbstractHigh‐electron‐mobility transistors (HEMTs) utilizing gallium nitride (GaN)‐based heterostructures are potential structures for the development of room temperature terahertz (THz) source and detectors. The corresponding material system also offers immense and exciting physical effects governing its behavior at THz frequencies. This behavioral simulation has been attempted for undoped aluminum gallium nitride/ aluminum nitride /GaN heterostructure for THz applications in the present work using technology computer‐aided design platform. Self‐consistent solutions of Schrodinger and Poisson equations are solved to calculate quantized energy states. The work also presents physics‐based device modeling of GaN HEMT structure using the simulated properties of heterostructure like electron mobility, two‐dimensional electron gas concentration, polarization charge concentration, conduction band energies, and so forth. Measurement‐based approach has been adopted to increase the reliability of the simulation and modeling. Various semiconductor characterization techniques have been utilized for this purpose. It is studied and presented that intersubband transition phenomenon is possible mode especially at THz frequency and can significantly contribute to extend the GaN‐HEMT operating frequency well beyond its present cutoff frequency to THz band.

Studying the Characteristics of Transistors Based on Gallium Nitride Heterostructures Grown by Ammonia Molecular Beam Epitaxy on Sapphire and Silicon Substrates

Ammonia molecular-beam epitaxy has been used to grow gallium nitride (GaN) transistor heterostructures on sapphire and silicon substrates. GaN transistors with a 1.2-mm periphery fabricated on substrates of both types exhibited similar high static characteristics: saturation current density above 0.75 A/mm, transconductance above 300 mS/mm, and breakdown voltage above 120 V. Measurements of the small-signal parameters showed that transistors based on silicon substrates possessed high gain in a frequency range up to 5 GHz; the specific output power at 1 GHz amounted to 5 W/mm for transistors on sapphire substrate and 2 W/mm for transistors on silicon substrate.

Effect of the Structural Quality of Quantum-Well Layers of Gallium-Nitride Heterostructures on Their Radiative Characteristics

The structural quality of GaN/GaInN/Al2O3 heterostructure layers and effect of their imperfection on the characteristics of emitters based on them are investigated. The layer imperfection is established by X-ray diffractometry. A new technique and an FD-24K photodiode-based device for determining the quantum yield are developed.

Low-noise amplifier for the range of 57–64 GHz with grounding holes through photolake layer

This paper is devoted to the development of a low-noise amplifier for the range of 57–64 GHz based on a gallium nitride heterostructure. The test HEMT-transistors based on gallium nitride are measured, which made it possible to create the transistor models: the Fujii and Pospeshalskii models. The basic diagram of the amplifier, which is composed of 4 cascades, is designed and the full electrodynamic calculation of the topology is carried out in CAD ADS. The prepared sample is measured, which showed its working ability in the required frequency range (the gain is larger than 16 dB, the coefficient of noise is smaller than 6.5 dB), and a good agreement between the results of the calculations and measurements is found. The technological stage used for the formation of through holes, which provide the common grounding plane of the circuit elements, is described.

Power switching transistors based on gallium nitride epitaxial heterostructures

The results of the development of power switching transistors based on epitaxial gallium nitride heterostructures to create an energy-efficient conversion technique are presented. The developed powerful GaN transistor operates in enrichment mode with unlocking threshold voltage V th = +1.2 V and a maximum drain-source current I ds = 0.15 A/mm at the drain-source voltage V ds = +8 V. The drain-source breakdown voltage in the closed state is V b = 300 V at the drain-source distance L ds = 8.5 μm and drain-source voltage V ds = 0 V.

History of GaN: High-Power RF Gallium Nitride (GaN) from Infancy to Manufacturable Process and Beyond

In the early 1990s, gallium nitride (GaN) was deemed an excellent, next generation, semiconductor material for high power/high frequency transistors based on the material parameters of bandgap, electron mobility, and saturated electron velocity. The lack of bulk GaN source material led to the need for GaN growth on mismatched substrates such as Si, SiC and sapphire, but fundamental material development controlled the pace of maturation of GaN technology for both electronic and optoelectronic applications. The development of GaN for RF electronics was significantly aided by the intense development that occurred in the race to first production of blue and, eventually, white light-emitting diodes (LEDs). Ultimately, advancements in the growth of device-grade aluminum gallium nitride (AlGaN)/GaN heterostructures culminated in the demonstration of record power density RF amplifiers.