Silicon photodiode with a grid <Emphasis Type="Italic">p-n</Emphasis> junction

Silicon photodiodes with a grid-structured p-region were studied. Analytical expressions for the capacitance of such photodiodes were derived. The influence of the cell sizes and diffusion length of minority carriers on the sensitivity of the silicon grid photodiode was analyzed in a spectral range of 0.6–1.0 μm. The experimental characteristics of photodiodes with a grid p-n junction with cell sizes of 50 and 110 μm are given. The factors controlling the spectral-characteristic features of these photodiodes are discussed.     

Terahertz self-induced oscillations in the injection <Emphasis Type="Italic">p-n</Emphasis> junction with fixed reverse bias

The results of numerical solutions of the complete equations of the diffusion-drift model (DDM) of Ge, Si and GaAs reverse-biased abrupt p-n junctions with injection of the constant-intensity electron flow into the p-region have been presented. The excitation mechanism of p-n junctions was examined and the factors affecting the frequency and amplitude of self-induced oscillations were established. The spectra of power and electron efficiency have been also presented. Abrupt Ge, Si and GaAs p-n junctions were shown to generate oscillations over the entire microwave range, while the second harmonic frequency could reach the terahertz (THz) range.     

Natural fluctuations in tunneling-current distribution over the area of a reverse-biased silicon <Emphasis Type="Italic">p-n</Emphasis> junction

The Monte Carlo method is used for calculating the distributions of the electric field, potential, and interband-tunneling probability over the area of a reverse-biased p-n junction, taking into account the discreteness of the charge distribution of ionized donors and acceptors. The calculations are carried out in a three-dimensional approximation on the basis of the principle of superposition of the electric fields of “ionized-donor-ionized-acceptor” ion pairs. It is shown that, in the region of clusters of three or more ion pairs with the characteristic distance of about half of the de-Broglie wavelength between them, an increase in the tunneling probability related to a local increase in the electric-field strength is observed.     

Movement of the boundary of a <Emphasis Type="Italic">p-n</Emphasis> junction in GaAs:Si under gyrotronic irradiation

It is shown that, by using a gyratron, it is possible to control the position of a p-n junction in an already fabricated light-emitting structure. A shift of the compensated region in the emitting structure based on GaAs:Si is caused by the motion of impurities in the field of thermoelastic stresses appearing in the course of sample cooling after gyrotronic irradiation.     

Waveguide photonic crystals with characteristics controlled with <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">i</Emphasis>-<Emphasis Type="Italic">n</Emphasis> diodes

A one-dimensional waveguide photonic structure—specifically, a photonic crystal with a controllable frequency characteristic—is designed. The central frequency of the spectral window of the photonic crystal can be tuned by choosing the parameters of disturbance of periodicity in the photonic crystal, whereas the transmission coefficient at a particular frequency can be controlled by varying the voltage at a p-i-n diode. It is shown that the possibility exists of using the waveguide photonic crystal to design a microwave device operating in the 3-cm-wavelength region, with a transmission band of 70 MHz at a level 3 dB and the transmission coefficient controllable in the range from −1.5 to −25 dB under variations in the forward voltage bias at the p-i-n diode from zero to 700 mV.     

Edge photoluminescence of single-crystal silicon with a <Emphasis Type="Italic">p-n</Emphasis> junction: Structures produced by high-efficiency solar cell technology

The systematic features and kinetics of edge photoluminescence of silicon structures produced by the high-efficiency solar cell technology is studied at different voltages applied to the p-n junction. It is shown that the effect of modulation of the edge photoluminescence intensity by a dc voltage applied to the p-n junction is qualitatively similar to the effect induced by excitation of photoluminescence by laser radiation at the wavelengths 658 and 980 nm. The possibility of modulating the edge photoluminescence power by varying the resistance parallel to the p-n junction is demonstrated. It is found that, at zero voltage, the rise time constant of the photoluminescence intensity far exceeds the decay time constant. However, as the dc forward current is increased, the decay time constant approaches the rise time constant. To interpret the results, the concepts of the second, more efficient saturable recombination channel coexisting with the common Shockley-Read-Hall recombination channel in the structure are developed. The study extends the functional capabilities of the luminescence technique in determining the effective lifetimes of charge carriers.     

Heating of charge carriers and rectification of current in asymmetrical <Emphasis Type="Italic">p-n</Emphasis> junction in a microwave field

The emf U _oc of hot charge carriers generated in an asymmetrical p-n junction in a microwave electromagnetic field is determined by hot holes despite the fact that the temperature of electrons is much higher than that of holes. It is established that the open-circuit voltage depends on the temperature of the carriers, which determine the total current through p-n junction.     

Stochastic Gradient Algorithm Under (<Emphasis Type="Italic">h</Emphasis>,<Emphasis Type="Italic">φ</Emphasis>)-Entropy Criterion

Motivated by the work of Erdogmus and Principe, we use the error (h,φ)-entropy as the supervised adaptation criterion. Several properties of the (h,φ)-entropy criterion and the connections with traditional error criteria are investigated. By a kernel estimate approach, we obtain the nonparametric estimator of the instantaneous (h,φ)-entropy. Then, we develop the general stochastic information gradient algorithm, and derive the approximate upper bound for the step size in the adaptive linear neuron training. Moreover, the (h,φ) pair are optimized to improve the performance of the proposed algorithm. For the finite impulse response identification with white Gaussian input and noise, the exact optimum φ function is derived. Finally, simulation experiments verify the results and demonstrate the noticeable performance improvement that may be achieved by the optimum (h,φ)-entropy criterion.     

Epitaxial Growth and Device Design Optimization of Full-Vertical GaN <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">i</Emphasis>-<Emphasis Type="Italic">n</Emphasis> Rectifiers

The optimization of growth parameters, epitaxial structure, and device design for full-vertical gallium nitride (GaN) p-i-n rectifiers grown on n-type 6H-SiC substrates employing AlGaN:Si conducting buffer layers have been studied. The Al _x Ga_1−x N:Si (x = ~0.1) nucleation layer is calibrated to be capable of acting as a good buffer layer for subsequent GaN growth as well as to provide excellent electrical properties. Two types of full-vertical devices were fabricated and compared: one without any current guiding and the other with the current guiding in the p-layer. The reverse breakdown voltage for rectifiers with a relatively thin 2.5-μm-thick i-region without p-current guiding was found to be over −330 V, while one with p-current guiding was measured to be over −400 V. Devices with p-current guiding structures exhibit reduced reverse leakage current by an order of magnitude >4 at −100 V.     

A <Emphasis Type="Italic">G</Emphasis><Subscript><Emphasis Type="Italic">m</Emphasis></Subscript><Emphasis Type="Italic">-C</Emphasis> continuous-time analog filter for IEEE 802.11 a/b/g/n wireless LANs

A CMOS transconductor for multi-mode wireless channel selection filter is presented. The linear transconductor is designed based on the flipped-voltage follower (FVF) circuit and an active resistor to achieve the transconductance tuning. The transconductance tuning can be obtained by changing the bias current of the active resistor. A third-order Butterworth low-pass filter implemented with the transconductors was designed by TSMC 0.18-μm CMOS process. The results show that the filter can operate with the cutoff frequency of 10–20 MHz. The tuning range would be suitable for the specifications of IEEE 802.11 a/b/g/n Wireless LANs under the consideration of saving chip areas. In the design, the maximum power consumption is 13 mW with the cutoff frequency of 20 MHz under a 1.8 V supply voltage.     

Thermoelectric Properties of NaCo<Subscript>2–<Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript>

NaCo₂O₄ has one of the highest figures of merit among all ceramic thermoelectric materials. Because of its large thermopower and low resistivity, the ceramic oxide NaCo₂O₄ is a promising candidate for potential thermoelectric applications. NaCo₂O₄ is, moreover, a ceramic compound with high decomposition temperature and chemical stability in air and it does not contain any toxic elements. Like all 3-d transition ions, Co ions have multiple spin and oxidation states. In this investigation, thermopower and electrical conductivity of NaCo₂O₄ as a function of substitution of Co by Fe ions were measured. Fe substitution for Co causes resistivity to increase, whereas the Seebeck coefficient remained nearly invariant, especially above 330 K. An erratum to this article can be found at     

Interfacial Reactions between Cu<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ni<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> Alloy Underbump Metallurgy and Sn-Ag-<Emphasis Type="Italic">z</Emphasis>Cu Solders

A reaction study of Cu _x Ni _y alloy (x = 0.2–0.95) under bump metallization (UBM) with Sn-Ag-zCu solder (z = 0–0.7) was conducted. Formation and separation of intermetallic compounds (IMCs), effect of Cu addition to the Cu _x Ni _y alloy and the solders, and compatibility of reaction products with currently available phase diagrams are extensively investigated. The increase of Cu content both in the Cu _x Ni _y alloy and in the solder promoted IMC growth and Cu _x Ni _y consumption; though, with regard to solder composition, the reverse trend was true of the solder reactions in the literature. The liquid + Cu₆Sn₅ area in the Sn-rich corner needs to be larger compared to the currently available Cu-Ni-Sn ternary phase diagram, and the maximum simultaneous soluble point of Ni and Cu in Sn needs also to be moved to the Ni-Sn side (e.g., Sn-0.6Cu-0.3Ni).     

Charge-Compensated <Emphasis Type="Italic">n</Emphasis>-Type Skutterudites

Ba+Yb double-filled n-type skutterudites with a modest degree of charge compensation by Fe on the Co lattice have been synthesized and compacted by spark-plasma sintering, and their thermoelectric properties evaluated at temperatures up to 800 K. Although this approach to making n-type skutterudites seems counterintuitive, the presence of Fe leads to a reduction in the thermal conductivity while it preserves a robust Seebeck coefficient. Consequently, a high ZT in excess of 1.3 was achieved at 800 K in these Fe-containing n-type skutterudite compounds.     

Magnetoconcentration effect on a base <Emphasis Type="Italic">pn</Emphasis> junction of a bipolar magnetotransistor

An experimentally discovered negative sensitivity effect related to the occurrence of the bulk magnetoconcentration effect on the well-substrate pn junction of a dual-collector lateral bipolar npn magnetotransistor with a diffused well serving as a base was studied by design and process simulation. It was established that the sign of sensitivity is determined by dividing electron and hole streams on the well-substrate pn junction in a magnetic field. Magnetic-field modulation of conductivity in the region of a bulk charge of the pn junction is analyzed.     

Planar <Emphasis Type="Italic">n</Emphasis>-on-<Emphasis Type="Italic">p</Emphasis> HgCdTe FPAs for LWIR and VLWIR Applications

Mainly driven by space applications, mercury cadmium telluride (MCT) focal-plane arrays (FPAs) have been successfully developed for very long wavelengths (λ _CO > 14 μm at 55 K). For this purpose, the standard n-on-p technology based on MCT grown by liquid-phase epitaxy (LPE) and involving vacancy doping has been modified to extrinsic doping by a monovalent acceptor. Due to the planar diode geometry obtained by ion implantation, most of the carrier generation volume is located in the p-type region with a thickness of approximately 8 μm. According to our understanding, the Shockley–Read centers connected with the Hg vacancies are thus significantly reduced. This situation should lead to longer minority-carrier lifetimes and smaller generation rates under equilibrium conditions, therefore yielding lower dark current. We indeed observe a reduction by a factor of approximately 15 by using extrinsic doping. Recent dark current data obtained in the temperature range from 55 K to 85 K on 288 × 384 FPAs with λ _CO(60 K) = 12 μm, either intrinsically or extrinsically doped, corroborate this finding. These data, new results on a 112 × 112 pixel demonstrator array with λ _CO(55 K) = 14.4 μm, and earlier measurements are compared with Tennant’s Rule 07 established for p-on-n technology.     

Electroluminescence in <Emphasis Type="Italic">p</Emphasis>-InAs/AlSb/InAsSb/AlSb/<Emphasis Type="Italic">p</Emphasis>(<Emphasis Type="Italic">n</Emphasis>)-GaSb type II heterostructures with deep quantum wells at the interface

Luminescent characteristics of asymmetric p-InAs/AlSb/InAsSb/AlSb/p-GaSb type II heterostructures with deep quantum wells at the heterointerface are studied. The heterostructures were grown by metalorganic vapor phase epitaxy. Intense positive and negative luminescence was observed in the range of photon energies of 0.3–0.4 eV with a forward and reverse bias, respectively. Dependences of the spectra and intensities for positive and negative luminescence on the pumping current and on the temperature are studied in the range of 77–380 K. It is established that, at a temperature higher than 75°C, intensity of negative luminescence surpasses that of positive luminescence by 60%. The suggested heterostructures can be used as lightemitting diodes (photodiodes) with switched positive and negative luminescence in the mid-IR spectral range of 3–4 μm.     

A filter of <Emphasis Type="Italic">H</Emphasis><Subscript>0<Emphasis Type="Italic">n</Emphasis></Subscript> modes in a multimode rectangular waveguide

A technique is developed for calculating the electrodynamic characteristics of a filter of H _0n modes in the case of various configurations of the filter and various combinations of its mechanical and electric parameters. In numerical computations, the complete set of the filter parameters is taken into account. It is shown that the number of absorbing elements in the filter can be reduced from three to two and that, simultaneously, the quality characteristics of the filter can be improved.     

Thermoelectric Properties of Half-Heusler Bismuthides ZrCo<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Ni<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Bi (<Emphasis Type="Italic">x</Emphasis> = 0.0 to 0.1)

The usefulness of half-Heusler (HH) alloys as thermoelectrics has been mainly limited by their relatively large thermal conductivity, which is a key issue despite their high thermoelectric power factors. In this regard, Bi-containing half-Heusler alloys are particularly appealing, because they are, potentially, of low thermal conductivity. One such a material is ZrCoBi. We prepared pure and Ni-doped ZrCoBi by a solid-state reaction. To evaluate thermoelectric potential we measured electrical resistivity (ρ = 1/σ) and thermopower (σ) up to 1000 K and thermal conductivity (κ) up to 300 K. Our measurements indicate that for these alloys resistivity of approximately a few mΩ cm and thermopower larger than a hundred μV K⁻¹ are possible. Low κ values are also possible. On the basis of these data we conclude that this system has a potential to be optimized further, despite the low power factors (α ² σT) we have currently measured.