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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)...
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...
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...
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...
Large current carrying capabilities of AlN/GaN/InN based heterostructures and high breakdown voltages make this materials system uniquely suited for applications in high power and/or high frequency electronic devices, including power amplifiers, broadband amplifiers, power switches, and radio frequency switches. AlGaN/GaN insulated gate transistors have additional advantages of extremely low leakage...
Recent advances in quantum dots for classical and non-classical light sources are presented. We have established MOCVD technology for InAs-based quantum dot lasers at 1.3 ??m and achieved ultra-low threshold in quantum dot lasers with photonic crystal nanocavity. In addition, single photon emitters at 1.55 ??m, GaN-based single photon sources operating at 200 K and high-Q photonic crystal nanocavity...
When AlGaN is grown on GaN template, crack networks invariably generate when the thickness of the AlGaN layers over GaN exceeds the critical value. We used thin high temperature deposited AlN layer (HT-AlN) as the interlayer between GaN template and AlGaN epilayer which was very effective in eliminating the cracks in AlGaN epilayer. AlGaN layers with high Al mole fractions were also grown. Characterization...
Magnetotransport study has been performed on AlxGa1-xN/GaN heterostructures at low temperatures and high magnetic fields. The magneto-intersubband scattering effect of the two-dimensional electron gas (2DEG) has been observed in the triangular quantum well at the heterointerface. It is found that the effective mass of the 2DEG have strong dependence on the magnetic field and the 2DEG density due to...
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