Theory of transient photocurrents in totally depleted semiconductors

Two categories of transient currents in totally depleted homogeniously doped semiconductors are treated mathematically. In the first category the transient current is completely space-charge limited while the current pulses in the second category arise from an injected charge reservoir where all of the injected charges immediately are under the influence of the electric field. Neglecting diffusion and trapping it is possible to obtain exact analytical solutions for the transients up to the transit time of the leading carriers. In the first category these transit times are obtained by numerical methods and presented graphically as a function of the ratio between the applied voltage and the depletion voltage of the semiconductor. In the second category implicit expressions are obtained from which the transit times can be calculated. For the completely space-charge limited case the analysis is carried on up to the transit time of the last carriers that start their travel at $\text{t = 0}$. In this part of the analysis the results are obtained numerically. Both majority carrier and minority carrier transients are considered.     

Threshold stresses for motion of dislocations in extrinsic semiconductors

It is shown that statistical fluctuations in the distribution of impurity atoms adsorbed at dislocations lead to the existence of a dislocation-mobility threshold with a magnitude σ_th dependent on temperature and interaction between impurities. In the low-temperature region, σ_th can significantly exceed the pinning-stress magnitude σ_pin determined by the average concentration of adsorbed impurities. The results of the calculation can also be used when describing the kinetics of one-dimensional systems of another physical nature.     

Effect of dynamic aging of dislocations on the deformation behavior of extrinsic semiconductors

The Alexander-Haasen theory of deformation in semiconductor crystals with low dislocation density was generalized by taking into account the effect of dynamic aging of dislocation caused by the impurity drag. The generalized theory explains some qualitative distinctions of the elastic-plastic transition in Czochralski-grown Si crystals from that in crystals of higher purity. Particularly, this concerns the dependence of the height of the yield-point peak on the initial dislocation density and the weakening of the strain-rate sensitivity of the yield stress.     

The role of nonequilibrium charge in generation of the thermopower in extrinsic semiconductors

A theory of the thermopower is developed with consideration for the nonequilibrium charge produced in a p-type semiconductor and metal contacts. It is shown that the thermopower is generated due to redistribution of the nonequilibrium charge between the metal contacts and semiconductor via transport of nonequilibrium electrons from the metal to the semiconductor through one of the surfaces and from the semiconductor to the metal through the other surface. In a p-type semiconductor sample with thickness smaller than the diffusion length, at certain surface parameters, the thermopower nonlinearly depends on the temperature difference.     

A special section on semiconductors

Semiconductors are inherently endowed with excellent photoelectric properties.Semiconductor materials are the foundation of modern electronics and many other devices including transistors, solar cells, many kinds of diodes,and digital and analog integrated circuits.     

A theorem on heat generation in semiconductors devices

An expression is derived which permits the calculation of the heat-density generation rate at any point in an operating semiconductor device in a time-dependent, temperature-dependent analysis.     

A note on resistor loops

Methods to directly measure the element values of a resistor loop without opening it are presented.     

A note on microprocessor typology

Our intentions is to simply show the usefulness of certain classic statistical tools in domains where such tools are rarely used. Certain of these tools bring about a new vision of a set of complex objects or systems: we have chosen, as a first step, to illustrate their potential on a simple set of micro-processors. It would be possible, in a further step, to apply those same techniques in other domains of computer science, in particular in the field of software metrics.The paper is divided in two parts: (1) Illustation of the techniques, through a practical example, which permit to reveal the essential characteristics of a family of micro-processors. (2) A short theorical summary of the statistical tools used.     

A note on IC-yield statistics

Expressions given by Moore and by Dingwall for relating integrated-circuit yield to area are compared and are given a common interpretation in terms of the composite model. The issue of large-chip yield projection is discussed, a subject that is still unclear because of the concave-up projections of the empirical curves, the linear projection of the composite model, and the concave-down projections of recent analytical models.     

A note on minimal repair

The cumulative function for the number of failures for a unit which is subjected to minimal repair after each failure is a nonstationary Poisson process. In this note, a simple method for obtaining this result is presented. A conditional probability approach is used for the derivation     

A note on heterojunction discontinuities

Recently, an analytic proof has been advanced to the effect that the intrinsic Fermi level of a heterojuntion is by necessity continuous across the interface joining two different semiconductors. Here we wish to show that the proof given is incorrect and that the solution of Poisson's equation for an intrinsic heterojunction on which the proof was based, does not yield any information on possible continuities or discontinuities of the intrinsic Fermi level.     

A note on reflector arrays

A Van Atta antenna array, which has a major lobe of the reradiated field in a direction retrograde to that of the incident wave for arbitrary directions of incidence, is analyzed in terms of the scattering matrix of the network interconnecting the antennas.     

A note on asymmetric turbo-codes

Little attention has been devoted in the literature to turbo-codes with nonidentical component codes. However, in order to optimize the performance of parallel concatenated schemes with respect to both the so called “error-floor” and the “waterfall” regions, the idea has certain advantages     

A note on volume holograms

A model describing the operation of volume phase holograms is studied. It is shown that due to hitherto disregarded effects the Bragg conditions are not automatically satisfied, and high efficiency of wave conversion may only be achieved under special circumstances.     

韩永飞的三次"上山下乡"

密安公司总经理韩永飞,话说草原当年——出国——回国,他所经历的三次“上山下乡”……     

A sea change for semiconductors

Skies were blue and trade winds were steady as the SS Semiconductor set sail in early 2001. The previous year's haul had set records, and forecasters were heralding yet another banner year. But powerful forces were to shake even this vessel's sturdy timbers. A low-pressure center caused by the bursting dot-com bubble and warm moist Y2K air from around the globe stirred up a storm so violent that it shredded the mainsail. Gales of corporate malfeasance from the southwest and typhoons of terrorism from the east swept wave after wave of stock-market volatility over the decks. While many of the crew were tossed overboard, cargo destined for distant ports sat idle in the holds. It was a long time before the winds grew calm enough for the crew to repair the battered boat and limp to port. But customers there, who had also been buffeted by the foul weather, were scarce. And the ship's officers were forced to sell their cargo at a fraction of its original value. Now, almost two years after the near-fatal voyage, forecasters are again predicting blue skies, and officers and crew are guardedly optimistic that good fortune awaits in the year ahead.     

A temperature noise model for extrinsic FETs

A resistor temperature noise model for FETs has been successfully applied to extrinsic FETs to predict the frequency dependence of minimum noise figure F_min and associated gain G_Aopt. The model gives a fixed relationship between F_min and G_Aopt with one fitting parameter T_d. An extensive comparison to published results shows that the majority of FETs can be modeled with effective T_d values (the temperature of the output resistor) between 300 and 700 K for all of the frequencies (8 to 94 GHz), gate lengths (0.8 to 0.1 μm), and material types examined. The analysis shows that InP-based MODFETs exhibit significantly lower F_min and higher G_Aopt than conventional and pseudomorphic GaAs-based MODFETs of the same gate length. The results suggest a high F_max is a key factor for low noise figure