There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Statistics for Spatial Data.

We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” nitrides (wurtzite and zinc-blende GaN, InN, and AlN, along with their alloys) and (2) “dilute” nitrides (zinc-blende ternaries and quaternaries in which a relatively small fraction of N is added to a host III–V material, e.g., GaAsN and GaInAsN). As in our more general review of III–V semiconductor band parameters [I. Vurgaftman et al., J. Appl. Phys. 89, 5815 (2001)], complete and consistent parameter sets are recommended on the basis of a thorough and critical review of the existing literature. We tabulate the direct and indirect energy gaps, spin-orbit and crystal-field splittings, alloy bowing parameters, electron and hole effective masses, deformation potentials, elastic constants, piezoelectric and spontaneous polarization coefficients, as well as heterostructure band offsets. Temperature an...

Band parameters for nitrogen-containing semiconductors

High-order harmonic generation is a nonlinear optical process that enables the creation of light pulses at frequencies much higher than that from a seed laser. The host medium for this interaction is typically a gas. Now, the process has been observed in a bulk crystalline solid with important implications for attosecond science.

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Observation of high-order harmonic generation in a bulk crystal

Calculation of Auger minority carrier lifetime in HgCdTe

Carbon related defects are readily incorporated in GaN due to its abundance during growth both with MBE and CVD techniques. Employing first-principles calculations we compute the migration barrier of neutral carbon interstitials in the wurtzite GaN crystal. The Minimum Energy Path (MEP) and the migration barriers of these defects are obtained using the Nudged Elastic Band (NEB) method with the climbing image modification (CI-NEB). In addition, the Dimer method is used to verify the results. The results yield a quantitative description of carbon diffusion in the crystal allowing for the determination of the most probable migration paths.

https://iopscience.iop.org/article/10.1088/1742-6596/633/1/012143/pdf

First-principles study of migration mechanisms and diffusion of carbon in GaN

An electrical and thermal study of submicron GaN multi-finger permeable base transistors (PBTs) is presented. Carrier transport in the intrinsic finger is studied with drift-diffusion and energy balance models, validated against ensemble Monte Carlo simulation; device performances are optimized through an aggressive geometrical scaling. Non-isothermal analysis of the complete multi-finger structure demonstrates the need for a mobility model whose temperature dependence is not confined to low-field parameters. The potential of GaN PBTs for microwave power applications is finally investigated by evaluating the relevant figures of merit.

http://iopscience.iop.org/article/10.1088/0268-1242/21/1/003/pdf

Theoretical investigation of GaN permeable base transistors for microwave power applications

The carrier dynamics in GaN under short‐pulse laser excitation is being investigated using a density‐matrix approach. Screened carrier‐phonon and carrier‐carrier interactions are considered in the generalized Monte Carlo simulation model. An analytical non‐parabolic band structure is included to describe the conduction band. It is found that due to large electron‐phonon scattering rates, the phonon replica does not appear in the electron distribution function.

Electron‐hole dynamics in GaN under short‐pulse laser excitation

In this work we analytically investigate the longitudinal optical conductivity of the C$_{2v}$ symmetric topological insulator. The conductivity expressions at $ T = 0 $ are derived using the Kubo formula and expressed as a function of the ratio of the Dresselhaus and Rashba parameters that characterize the low-energy Hamiltonian. We find that the longitudinal inter-band conductivity vanishes when Dresselhaus and Rashba parameters are equal in strength, also called the persistent spin helix state. The calculations are extended to obtain the frequency-dependent real and imaginary components of the optical conductivity for the topological Kondo insulator SmB$_{6}$ which exhibits C$_{2v}$ symmetric and anisotropic Dirac cones hosting topological states at the $ \overline{X} $ point on the surface Brillouin zone.

Enrico Bellotti

Papers

Calculation of Auger minority carrier lifetime in HgCdTe

First-principles study of migration mechanisms and diffusion of carbon in GaN

Theoretical investigation of GaN permeable base transistors for microwave power applications

Electron‐hole dynamics in GaN under short‐pulse laser excitation

Intrinsic optical conductivity of a C$_{2v}$ symmetric topological insulator