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

A comparison between different Monte Carlo models in simulation of hole transport in 4H-SiC

This work presents a numerical simulation study of HgCdTe-based avalanche photodetectors (APDs). The two-dimensional model used is based on a full-band Monte Carlo approach in which the electronic structure is computed using a nonlocal empirical pseudopotential model with spin–orbit corrections. The carrier–phonon scattering rates have been computed from first principles using a rigid pseudo-ion model. The most attractive feature of these devices is the potential for single-carrier ionization when electrons are used as the primary injection carrier. For this reason, this work focuses on two front-illuminated (electron-injection) device structures: a planar diffused PIN structure and a planar diffused PN photodiode with guard rings. To predict the performance of these APDs, the electron multiplication gain has been studied as a function of the position where photogenerated carriers are injected and as a function of the curvature of the p-type diffusion region. We find that, in the diffused PIN structure, the limited lateral spatial extent of the high-electric-field region leads to a reduction of the multiplication gain from the center of the device to the periphery. Furthermore, the higher the curvature, the more abruptly the gain decreases. For the simple PN structure, we find that the presence of the guard rings removes the high electric field from the surface and induces a more gradual roll-off of the gain from the center of the device to the periphery.

A 2D Full-Band Monte Carlo Study of HgCdTe-Based Avalanche Photodiodes

A key design feature of P+-on-n HgCdTe detectors is the depth of the p-type region Normally, homojunction architectures are utilized where the p-type region extends into the narrow-gap absorber layer This facilitates the collection of photo-carriers from the absorber layer to the contact; however, this may result in excess generation-recombination (G-R) current if defects are present Alternatively, properly adopting a heterojunction architecture confines the p-type region (and the majority of the electric field) solely to the wide-gap layer Junction placement is critical since the detector performance is now dependent on the following sensitivity parameters: p-type region depth, doping, valence band offset, lifetime and detector bias Understanding the parameter dependence near the hetero-metallurgical interface where the compositional grading occurs and the doping is varied as either a Gaussian or error function is vital to device design Numerical modeling is now essential to properly engineer the electric field in the device to suppress G-R current while accounting for the aforementioned sensitivity parameters The simulations reveal that through proper device design the p-type region can be confined to the wide-gap layer, reducing G-R related dark current, without significantly reducing the quantum efficiency at the operating bias V = -0100V

Heterojunction depth in P+-on-n eSWIR HgCdTe infrared detectors: generation-recombination suppression

The growing importance of In 0:18 Al 0:82 N stems from the fact that it can be grown lattice matched to GaN and for its potential applications in a large number of electronics and optoelectronics devices. In this work we employed
a full band Monte-Carlo approach to study the carrier transport properties of this alloy. We have computed the temperature and doping dependent electron and hole mobilities and drift velocities. Furthermore, for both sets of transport coefficients we have developed a number of analytical expressions that can be easily incorporated in drift-diffusion type simulation codes.

A full band Monte-Carlo study of carrier transport properties of InAlN lattice matched to GaN

The intrinsic carrier recombination lifetime in relaxed and strained InAs1−xSbx alloys is investigated using the full-band Green's function theory. By computing the phonon-perturbed electron self-energy of the system, both direct and phonon-assisted indirect Auger and radiative processes are studied as functions of antimony molar fractions, lattice temperatures and applied in-plane biaxial strains. To improve the overall accuracy of the calculation, an empirical pseudopotential band structure for the alloy is also fitted to the measured band extrema and effective masses under different biaxial strains. A set of effective screened potentials valid for all the needed antimony fractions x and biaxial strains ϵ, therefore, is obtained and applied to the calculation. The results showed reduced total Auger recombination rates and enhanced radiative recombination rates in InAsSb alloys at room temperature when a compressive strain is applied. Furthermore, the study on the widely employed mid-wavelength infrared detector material,InAs0.91Sb0.09, strained by an InAs substrate, demonstrated that much longer minority carrier lifetime can be achieved compared to that in the lattice-matched situation when the lattice temperature is above 200 K.

Enrico Bellotti

Papers

A comparison between different Monte Carlo models in simulation of hole transport in 4H-SiC

A 2D Full-Band Monte Carlo Study of HgCdTe-Based Avalanche Photodiodes

Heterojunction depth in P+-on-n eSWIR HgCdTe infrared detectors: generation-recombination suppression

A full band Monte-Carlo study of carrier transport properties of InAlN lattice matched to GaN

Optical absorption and intrinsic recombination in relaxed and strained InAs1–xSbx alloys for mid-wavelength infrared application