Bone grafts and biomaterials substitutes for bone defect repair: A review.

Fundamentals and advances in magnesium alloy corrosion

Synthesis methods for nanosized hydroxyapatite with diverse structures.

GaN high-electron-mobility-transistors (HEMTs) on SiC were fabricated with field plates of various dimensions for optimum performance Great enhancement in radio frequency (RF) current-voltage swings was achieved with acceptable compromise in gain, through both reduction in the trapping effect and increase in breakdown voltages When biased at 120 V, a continuous wave output power density of 322 W/mm and power-added efficiency (PAE) of 548% at 4 GHz were obtained using devices with dimensions of 055/spl times/246 /spl mu/m/sup 2/ and a field-plate length of 11 /spl mu/m Devices with a shorter field plate of 09 /spl mu/m also generated 306 W/mm with 496% PAE at 8 GHz Such ultrahigh power densities are a dramatic improvement over the 10-12 W/mm values attained by conventional gate GaN-based HEMTs

30-W/mm GaN HEMTs by field plate optimization

The macroscopic nonlinear pyroelectric polarization of wurtzite AlxGa1-xN, InxGa1-xN and AlxIn1-xN ternary compounds (large spontaneous polarization and piezoelectric coupling) dramatically affects the optical and electrical properties of multilayered Al(In)GaN/GaN hetero-, nanostructures and devices, due to the huge built-in electrostatic fields and bound interface charges caused by gradients in polarization at surfaces and heterointerfaces. Models of polarization-induced effects in GaN-based devices so far have assumed that polarization in ternary nitride alloys can be calculated by a linear interpolation between the limiting values of the binary compounds. We present theoretical and experimental evidence that the macroscopic polarization in nitride alloys is a nonlinear function of strain and composition. We have applied these results to interpret experimental data obtained in a number of InGaN/GaN quantum wells?(QWs) as well as AlInN/GaN and AlGaN/GaN transistor structures. We find that the discrepancies between experiment and ab initio theory present so far are almost completely eliminated for the AlGaN/GaN-based heterostructures when the nonlinearity of polarization is accounted for. The realization of undoped lattice-matched AlInN/GaN heterostructures further allows us to prove the existence of a gradient in spontaneous polarization by the experimental observation of two-dimensional electron gases?(2DEGs). The confinement of 2DEGs in InGaN/GaN QWs in combination with the measured Stark shift of excitonic recombination is used to determine the polarization-induced electric fields in nanostructures. To facilitate inclusion of the predicted nonlinear polarization in future simulations, we give an explicit prescription to calculate polarization-induced electric fields and bound interface charges for arbitrary composition in each of the ternary III-N alloys. In addition, the theoretical and experimental results presented here allow a detailed comparison of the predicted electric fields and bound interface charges with the measured Stark shift and the sheet carrier concentration of polarization-induced 2DEGs. This comparison provides an insight into the reliability of the calculated nonlinear piezoelectric and spontaneous polarization of group III nitride ternary alloys.

http://iopscience.iop.org/article/10.1088/0953-8984/14/13/302/pdf

Pyroelectric properties of Al(In)GaN/GaN hetero- and quantum well structures

: Channel recessed 4H-SiC MESFETs have demonstrated excellent small signal characteristics and the effect of SiN4%4 passivation on these devices has been studied in this work A saturated current of 250-270 mA/mm and a maximum transconductance of 40-45 mS/mm were measured for these devices The 3-terminal breakdown voltage Vds ranges from 120 V to more than 150 V, depending on gate-drain spacing 2 x 200 devices with 045 micronm gate length show high Ft of 145 GHz and F(max) of 40 GHz After Si3N4 passivation, the output power and PAE were increased by 40% and 16%, respectively, for CW power measurement Other measurements, such as, the change in surface potential and the dispersion of the drain current make it clear that the passivation of SiC MESFETs reduces the surface effects and enhances the RF power performance by suppressing the instability in DC characteristics

Channel Recessed 4H-SiC MESFETs with F t of 14.5GHz and F max of 40GHz

Parasitic Resistance Effects on Mobility Extraction of Normally-off AlGaN/GaN Gate-recessed MISHFETs

Electrical gate and drain characteristics of double heterostructure InAlAs/InGaAs pseu- domorphic HEMTs have been investigated under sub-bandgap photonic excitation (hν<Eg). Drain (VDS)-, gate(VGS)-, and optical power(Popt)-dependent variation of the abnormal gate leakage current and associated physical mechanisms in the PHEMTs have been characterized. Peak gate voltage (VGS,P) and the onset voltage for the impact ionization ( VGS,II) have been extracted and empirical model for their dependence on the VDS and Popt have been proposed. Anomalous gate and drain current, both under dark and under sub-bandgap photonic excitation, have been modeled as a parallel connection of high performance PHEMT with a poor satellite FET as a parasitic channel. Sub-bandgap photonic characteri- zation, as a function of the optical power with hν=0.799eV, has been comparatively combined with those under dark condition for characterizing the bell-shaped negative humps in the gate current and subthreshold drain leakage under a large drain bias.

Electrical Characteristics of InAlAs/InGaAs/InAlAs Pseudomorphic High Electron Mobility Transistors under Sub-Bandgap Photonic Excitation

Coil Encasing and VPI Process of the KSTAR Toroidal Field Magnet System

In this paper, a new photonic gated-diode method is proposed to extract the energy-dependent and spatial distributions of interface states in MOSFETs. For the photonic current–voltage (I–V) characterization of MOSFETs, an optical source with a photon energy less than the silicon bandgap (hν=0.95eV<Eg=1.12eV) is employed for the characterization of interface states (Eit) distributed in the photo-responsive energy band (EC-0.95≤Eit≤EC) in MOS systems with a polysilicon gate. The proposed novel method is simple and feasible for accurate extraction of interface traps MOSFETs.

Photonic Gated-Diode Method for Extracting the Energy-Dependent and the Spatial Distributions of Interface States in MOSFETs

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