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We report on an AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT) using thermal oxidation of electron-beam deposited aluminum as the gate dielectric. This novel dielectric deposition process is simple, and less expensive than electron cyclotron resonance (ECR) plasma oxidation of Al or atomic layer deposited (ALD) Al2O3. The X-ray Photoelectron Spectroscopy (XPS) Ols...
The recent discovery of the potential and charge modulation by fluorine ions incorporated in III-nitride heterojunction FETs has opened up numerous new opportunities of realizing desired device performance and fabricating integrated circuits with desirable circuit configurations. The most significant development based on the fluorine plasma ion implantation technology is the demonstration of self-aligned...
GaN/AlGaN device technologies are reviewed aiming at the applications to power switching systems. SL (Super Lattice) capping and QA (Quaternary Alloy) over-layer techniques have been developed to reduce the on-resistance of GaN/ AlGaN HFET. Further, we achieved GaN on Silicon epitaxial growth technology with almost the same mobility keeping the same 2DEG density, which will make the cost comparable...
The influences of applied electrical fields on the absorption coefficient and subband energy distances of intersubband transitions (ISBTs) in AlN/GaN coupled double quantum wells (CDQWs) have been investigated by solving the Schrodinger and Poisson equations self-consistently. It is found that the absorption coefficient of the ISBT between the ground state and the second excited state (1odd-2odd)...
For superluminescent diodes fabricated on the substrate with five 6 nm InGaAsP quantum wells and two 15 nm InGaAsP quantum wells, a very broad emission spectrum is obtained. The spectral width is nearly 400 nm, covering the range from 1250 nm to 1650 nm.
In this paper fabrication of high power light emitting diodes (LEDs) with combined transparent electrodes on both P-GaN and N-GaN have been demonstrated. Simulation and experimental results show that comparing with traditional metal N electrodes the efficacy of LEDs with transparent N electrode is increased by more than 10% and it is easier in process than the other techniques. Further more, combining...
This work reports, high electron mobility transistors (HEMTs) using a dilute antimony In0.2Ga0.8AsSb channel, grown by molecular beam epitaxy (MBE) system. Introducing the surfactant-like Sb atoms during growth of the InGaAs/GaAs quantum well (QW) was devised to effectively improve the channel confinement capability and the interfacial quality within the InGaAsSb/GaAs QW heterostructure, resulting...
AlGaN/AlN/GaN/InGaN/GaN double heterojunction high electron mobility transistors (DH-HEMTs) structures with improved buffer isolation have been investigated. The structures were grown by MOCVD on sapphire substrate. AFM result of this structure shows a good surface morphology with the root-mean-square roughness (RMS) of 0.196 nm for a scan area of 5 ??m?? 5 ??m. A mobility as high as 1950 cm2/Vs with...
A HBT MIC power amplifier with power combining based on InGaP/GaAs HBT was developed and measured for the application of C-band. The amplifier consists of two 2??480 ??m emitter area InGaP/GaAs HBT power transistors. Microstripe line parallel matching networks were used to divide and combine the power. A parallel RC stabilization network was used to suppress the self-oscillation. By biasing the amplifier...
The leakage current mechanism in Schottky contacts (SCs) to Al0.25Ga0.75N/GaN heterostructures incorporated by thin high-temperature (HT) AlN interlayer has been investigated using current-voltage measurements, atomic force microscopy, and deep level transient spectroscopy. The HT AlN interlayer thickness has a significant effect on the leakage current in SCs. The leakage current density is reduced...
200 nm thick InxAl1-xN epilayers around lattice-matched to GaN were grown on GaN templates by MOCVD. The elastic strain, surface morphology and crystalline quality of the InxAl1-xN were evaluated by high resolution X-ray diffraction (HRXRD) measurements, scanning electron microscopy (SEM) images and Rutherford backscattering spectroscopy (RBS) analyses. The strain effect, as while as the influences...
Performances of AlGaN/GaN HFETs have much improved recently and very high potential of this heterostructure for high power and high frequency electronic devices has been verified. Application of new device technologies such as field plate, recessed gate, digital pre-distortion circuit and dual field plate was essential to realize such high device performances both at 2 GHz, 5GHz and 26 GHz. However,...
Low resistance Ti/Al/Ni/Au Ohmic contact to (NH4)2Sx treated n-type GaN has been studied in the temperature range from 25??C to 600??C It is found that the specific contact resistivity ??c of the sample treated with (NH4)2Sx solution for 5 min at 90??C decreases with increasing measuring temperature, while the ??c of the sample treated with (NH4)2Sx solution for 25 min at 90??C increases with increasing...
Morphology and microstructure evolution of Al0.3Ga0.7N epilayers grown on GaN/sapphire templates with low-temperature (LT) AlN interlayers (ILs) by means of metal organic chemical vapor deposition have been investigated by transmission electron microscopy and atomic force microscopy. It is found that the IL improves the surface morphology, and suppresses edge-type threading dislocations (TDs). When...
A detailed reaction-transport model was studied in a showerhead reactor for metal organic chemical vapor deposition of GaN film by using computational fluid dynamics simulation. It was found that flat flow lines without swirl are crucial to improve the uniformity of the film growth, and thin temperature gradient above the suscptor can increase the film deposition rate. By above-mentioned research,...
Evidence of mobile, positive charges (holes) on the top surface of GaN HFET is found by conducting C-V measurement of a MIS HEMT diode. Significantly improved understanding of the effects of built-in electric polarization and doping on III-nitride heterojunction device structure electrical properties has been made. The result also confirms that removal of surface mobile holes is the root cause for...
Magnetotransport properties of the two-dimensional electron gas (2DEG) in the triangular quantum well at AlxGa1-xN/GaN heterointerfaces have been investigated by means of temperature dependent Shubnikov-de Haas (SdH) measurements at low temperatures and high magnetic fields under illumination. After the illumination of the heterostructures, the 2DEG concentration increases and the SdH oscillation...
Fluorine plasma ion implantation is a robust technique that enables shallow implantation of fluorine ions into group III-nitride epitaxial structures. This technique has been used to achieve robust threshold control of the AlGaN/GaN high electron mobility transistors (HEMTs) and led to the realization of self-aligned enhancement-mode devices. To reveal the atomic scale interactions and provide a modeling...
We evaluate the performance of GaAs-GaP core-shell nanowire field effect transistors by employing a semiclassical ballistic transport model and a k??p calculation of the valence band structures including the strain effect. We find that the strain will induce substantial modulation on the nanowire valence band structures and this modulation will push more conduction channels into the bias window as...
To improve the performances of ohmic contacts for GaN devices, a novel multilayer Ti/Al-based metal scheme (Ti/Al/Ti/Al/Ti/Al/Ti/Al/Ni/Au) on undoped AlGaN/GaN heterostructures was employed. A contact with ??c (specific contact resistance) of 8.74E-07 ????cm2, Rc of 0.22 ????mm was demonstrated. Ohmic contacts with the novel metal structure were measured with I-V, SEM, HRTEM to show their properties...
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