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.

/pdf/observation-of-high-order-harmonic-generation-in-a-bulk-2ujjcse9va.pdf

Observation of high-order harmonic generation in a bulk crystal

We have studied the performance of deep-UV avalanche photodetectors based on AlGaN alloys. We have evaluated the carrier multiplication gains and excess noise factors using a model based on recurrence equations and activated ionization coefficients derived from a full-band Monte Carlo model. We find that for devices with Al 0.4 Ga 0.6 N the excess noise factor increases linearly with the gain. When Al 0.6 Ga 0.4 N is used, the excess noise factor is significantly reduced. Finally, from the analysis of the possible device configurations, electric field distribution and its magnitude, we find that the fabrication of these devices will be challenging and alternative approaches should be considered.

Numerical simulation of deep-UV avalanche photodetectors

This paper presents one-dimensional numerical simulations and analytical modeling of ideal (only diffusion current and only Auger-1 and radiative recombination) InAs nBn detectors having n-type barrier layers, with donor concentrations ranging from 1.8×1015 to 2.5×1016 cm-3. We examine quantitatively the three space charge regions in the nBn detector with an n-type barrier layer (BL), and determine criteria for combinations of bias voltage and BL donor concentration that allow operation of the nBn with no depletion region in the narrow-gap absorber layer (AL) or contact layer (CL). We determine the quantitative characteristics of the valence band barrier that is present for an n-type BL. From solution of Poisson’s equation in the uniformly doped BL, we derive analytical expressions for the valence band barrier heights versus bias voltage for holes in both the AL and the CL. These expressions show that the VB barrier height varies linearly with the BL donor concentration and as the square of the BL width. Using these expressions, we constructed a phenomenological equation for the dark current density versus bias voltage which agrees reasonably well with the shape of the J(V) curves from numerical simulations. Our simulations suggest that the nBn detector should be able to be operated at or near zero-bias voltage.

Numerical simulation of InAs nBn infrared detectors with n-type barrier layers

A novel room-temperature negative differential resistance (NDR) effect is proposed, theoretically analyzed, and quantitatively modeled for short-wave infrared (SWIR) HgCdTe photodiode detectors in dense double-layer planar heterostructure arrays with a 2.5 $\mu \text{m}$ cutoff at 300 K. The predicted NDR results from nonequilibrium minority carrier suppression—with associated Auger suppression and negative luminescence—imposed by dense array geometry under uniform reverse bias. Using three-dimensional quantitative modeling, we evaluate representative dark current–voltage characteristics at different array pitch values. The predicted dark current and NDR resulting from structural variations in junction radius are consistent with the analytic dense array lateral diffusion current suppression model. The NDR effect and its relation to geometric parameters should be considered when attempting to minimize dark current in high-temperature SWIR HgCdTe photodiode arrays.

Negative Differential Resistance in Dense Short Wave Infrared HgCdTe Planar Photodiode Arrays

Disorder-Induced Degradation of Vertical Carrier Transport in Strain-Balanced Antimony-Based Superlattices

In this paper we describe a model for a fully numerical Monte Carlo simulator and the required inputs, which include the calculation of numerical phonon scattering rates and the electronic bandstructure. The model is material-independent, and it therefore provides great flexibility in the ability to characterize many semiconductor materials, including the III–V and III-Nitride materials. All of the principal ingredients of the Monte Carlo model are determined numerically from first principles with one exception, that of the acoustic deformation potential. The determination of the acoustic deformation potential, which specifies the relative strength of the acoustic phonon scattering rate, affects the calculated results. We introduce a methodical approach for its selection and examine the sensitivity of the primary calculated transport quantities on its magnitude. Specifically, we examine how the choice of the acoustic deformation potential, in a completely numerical Monte Carlo model, affects the calculated velocity field curve, average energy, and impact ionization coefficients. Calculations are made for both bulk GaAs and 3C-SiC and for a representative GaAs MESFET structure. It is found that the acoustic deformation potential needs to be energy dependent and that it requires at least two values, one for intra-band transitions and one for inter-band transitions. It is further found that through the use of the fully numerical model introduced here, reliable transport-related results may be obtained for bulk material as well as representative devices using only the acoustic deformation potential as the single adjustable parameter.

Enrico Bellotti

Papers

Numerical simulation of deep-UV avalanche photodetectors

Numerical simulation of InAs nBn infrared detectors with n-type barrier layers

Negative Differential Resistance in Dense Short Wave Infrared HgCdTe Planar Photodiode Arrays

Disorder-Induced Degradation of Vertical Carrier Transport in Strain-Balanced Antimony-Based Superlattices

A General Monte Carlo Model Including the Effect of the Acoustic Deformation Potential on the Transport Properties