Investigation of AlGaN Channel HEMTs on β-Ga2O3 Substrate for High-Power Electronics

The wider bandgap AlGaN (Eg > 3.4 eV) channel-based high electron mobility transistors (HEMTs) are more effective for high voltage operation. High critical electric field and high saturation velocity are the major advantages of AlGaN channel HEMTs, which push the power electronics to a greater operating regime. In this article, we present the DC characteristics of 0.8 µm gate length (LG) and 1 µm gate-drain distance (LGD) AlGaN channel-based high electron mobility transistors (HEMTs) on ultra-wide bandgap β-Ga2O3 Substrate. The β-Ga2O3 substrate is cost-effective, available in large wafer size and has low lattice mismatch (0 to 2.4%) with AlGaN alloys compared to conventional SiC and Si substrates. A physics-based numerical simulation was performed to investigate the DC characteristics of the HEMTs. The proposed HEMT exhibits sheet charge density (ns) of 1.05 × 1013 cm−2, a peak on-state drain current (IDS) of 1.35 A/mm, DC transconductance (gm) of 277 mS/mm. The ultra-wide bandgap AlGaN channel HEMT on β-Ga2O3 substrate with conventional rectangular gate structure showed 244 V off-state breakdown voltage (VBR) and field plate gate device showed 350 V. The AlGaN channel HEMTs on β-Ga2O3 substrate showed an excellent performance in ION/IOFF and VBR. The high performance of the proposed HEMTs on β-Ga2O3 substrate is suitable for future portable power converters, automotive, and avionics applications.

Diamond/GaN HEMTs: Where from and Where To?

Gallium nitride is a wide bandgap semiconductor material with high electric field strength and electron mobility that translate in a tremendous potential for radio-frequency communications and renewable energy generation, amongst other areas. However, due to the particular architecture of GaN high electron mobility transistors, the relatively low thermal conductivity of the material induces the appearance of localized hotspots that degrade the devices performance and compromise their long term reliability. On the search of effective thermal management solutions, the integration of GaN and synthetic diamond with high thermal conductivity and electric breakdown strength shows a tremendous potential. A significant effort has been made in the past few years by both academic and industrial players in the search of a technological process that allows the integration of both materials and the fabrication of high performance and high reliability hybrid devices. Different approaches have been proposed, such as the development of diamond/GaN wafers for further device fabrication or the capping of passivated GaN devices with diamond films. This paper describes in detail the potential and technical challenges of each approach and presents and discusses their advantages and disadvantages.

Impact of n-Doping Mechanisms on the Molecular Packing and Electron Mobilities of Molecular Semiconductors for Organic Thermoelectrics

Electrical conductivity is one of the key parameters for organic thermoelectrics and depends on both the concentration and mobility of charge carriers. To increase the carrier concentration, molecular dopants have to be added into organic semiconductor materials, whereas the introduction of dopants can influence the molecular packing structures and hence carrier mobility of the organic semiconductors. Herein, we have theoretically investigated the impact of different n-doping mechanisms on molecular packing and electron transport properties by taking N-DMBI-H and Q-DCM-DPPTT respectively as representative n-dopant and molecular semiconductor. The results show that when the doping reactions and charge transfer spontaneously occur in the solution at room temperature, the oppositely charged dopant and semiconductor molecules will be tightly bound to disrupt the semiconductor to form long-range molecular packing, leading to a substantial decrease of electron mobility in the doped film. In contrast, when the doping reactions and charge transfer are activated by heating the doped film, the molecular packing of the semiconductor is slight affected and hence the electron mobility remains quite high. This work indicates that thermally-activated n-doping is an effective way to achieve both high carrier concentration and high electron mobility in n-type organic thermoelectric materials.

Interlayer electron flow and field shielding in twisted trilayer graphene quantum dots

While multilayer graphene (MLG) possesses excellent intralayer electron mobility, its interlayer electrical conductance exhibits great diversity that results in exotic phenomena and various applications in electronic devices. Driven by a...

InP and InGaAs grown on InP substrate by molecular beam epitaxy

InP and InGaAs epitaxial layers on InP substrates using molecular beam epitaxy (MBE) have been studied. Carrier concentration and mobility of InP and InGaAs are found that are strongly correlated with the growth temperature and V/III ratio. The InGaAs layers using As2 were compared with the layers grown using As4 from a Riber standard cracker cell. When As4 is used, the highest electron mobility of InGaAs is 3960 cm2/(V·s) with the V/III ratio of 65. When converted to As2, the V/III ratio with the highest electron mobility decreased to 20. With the arsenic cracker temperature decreased from 950 ℃ to 830 ℃, the electron mobility increased from 4090 cm2/(V • s) to 5060 cm2/(V • s).

Optimization based on electro-thermo-mechanical modeling of the high electron mobility transistor (HEMT)

The electro-thermomechanical modeling study of the High Electron Mobility Transistor (HEMT) has been presented, all the necessary equations are detailed and coupled. This proposed modeling by the finite element method using the Comsol multiphysics software, allowed to study the multiphysics behaviour of the transistor and to observe the different degradations in the structure of the component. Then, an optimization study is necessary to avoid failures in the transistor. In this work, we have used the Covariance Matrix Adaptation-Evolution Strategy (CMA-ES) method to solve the optimization problem, but it requires a very important computing time. Therefore, we proposed the kriging assisted CMA-ES method (KA-CMA-ES), it is an integration of the kriging metamodel in the CMA-ES method, it allows us to solve the problem of optimization and overcome the constraint of calculation time. All these methods are well detailed in this paper. The coupling of the finite element model developed on Comsol Multiphysics and the KA-CMA-ES method on Matlab software, allowed to optimize the multiphysics behaviour of the transistors. We made a comparison between the results of the numerical simulations of the initial state and the optimal state of the component. It was found that the proposed KA-CMA-ES method is efficient in solving optimization problems.