Small-signal theory of transit-time diodes

Transit-time diodes, in which the effects of carrier diffusion and generation or recombination are not important, have recently been investigated both theoretically and experimentally. The impedance of these devices, mainly due to one type of carriers, has been computed by several authors with different simplifying assumptions. In this paper a more general expression of the impedance of the transit-time diode is given, accounting for the spatial non-uniform d.c. distributions of the electric field and of the carrier velocity, and by allowing any dependance of the carrier mobility on the d.c. electric field. The impedance is given in closed form in the case where the mobility is constant. The impedance of a metal-semiconductor-metal structure is then computed, and the frequency and bias range over which a negative resistance arises is found to be consistent with known experimental data.     

Nonlinear theory for laser diodes

This paper outlines a nonlinear theory for the output power vs excitation current of an injection diode laser. The dependence upon electric field amplitude of effective negative conductivity in the region of inverted population derived and used to determine the level of steady oscillation in the quasilinear approximation (nonlinear conduction current small compared with displacement current). This level is simply related to the output power. A field dependent negative conduction current is derived from the negative conductivity which indicates that, in the quasilinear approximation, the presence of two modes with the same polarization will be an unstable situation; one mode will grow at the expense of the other.     

Field correlation diffraction theory of the symmetrical cassegrainian antenna

The received field as focused by the parabolic main reflector of a Cassegrainian antenna at the surface of an arbitrary profile subreflector is calculated by a spherical wave expansion. This facilitates the application of the field correlation principle and leads to an expression for aperture efficiency taking into account diffraction effects. A comparison is made with numerical results previously published or obtained by other methods. The potential advantage of the technique is the speed of computation and the capability for synthesis as well as analysis of reflector shapes.     

Point-contact diodes in terms of p-n junction theory

A "formed" n-type germanium point-contact diode is qualitatively reminiscent of an idealized model that comprises an abrupt hemispherical p-n junction, both regions of which may have moderate resistivity, terminated on the inner (p) and outer (n) sides by hemispherical ohmic contacts. The extent to which this model can be justified quantitatively is investigated. Low-injection analyses of the static and small-signal, frequency-dependent properties suggest that the model is capable of predicting the corresponding experimentally-observed behavior. Consideration of space-charge-layer widening with reverse bias allows the computation of breakdown and punch-through voltages, which correspond in magnitude range to the observed peak inverse voltages of formed germanium point contacts. A high-injection analysis of the static forward characteristic indicates approximate agreement between theory and experiment, even for the nonlinear spreading resistance.     

A CMOS image sensor with a double-junction active pixel

A CMOS image sensor that employs a vertically integrated double-junction photodiode structure is presented. This allows color imaging with only two filters. The sensor uses a 184*154 (near-QCIF) 6-transistor pixel array at a 9.6-/spl mu/m pitch implemented in 0.35-/spl mu/m technology. Results of the device characterization are presented. The imaging performance of an integrated two-filter color sensor is also projected, using measurements and software processing of subsampled images from the monochrome sensor with two color filters.     

Analytical theory of stable domains in high-doped Gunn diodes

The form, amplitude and width of the stable domain are determined analytically for the case of high doping level (n0 > 5.0×1015cm?3).     

光伏型光电探测器漂移-扩散模型的改进

提出了改进的描述光伏型半导体光电探测器中载流子输运的漂移-扩散模型,该模型能适合更高强度的激光辐照,可以模拟光生载流子的长时间过程。依据该模型,对光伏型探测器进行了模拟计算,得到了激光辐照下探测器的动态响应规律、探测器温升以及材料参数对探测器响应的影响。     

Properties and design theory of ultrafast GaAsmetal-semiconductor-metal photodetector with symmetrical Schottkycontacts

A GaAs metal-semiconductor-metal photodetector fabricated in a symmetrical and interdigital Schottky contact structure on a semi-insulating GaAs substrate is discussed. The device exhibits a high-speed response and a very low dark current, even with a moderate size (200 μm²). Ultrafast responsivity is due to the high drift velocity of the photoelectrons and low capacitance. A design theory for optimum performance which includes a compromise between the circuit time constant and the transit time is described     

Theory of conduction in polysilicon: Drift-diffusion approach in crystalline-amorphous-crystalline semiconductor system—Part II: General I-V theory

A general model for conduction in polysilicon is presented for arbitrary applied voltage. The model incorporates the effect of mobile carrier redistribution under bias and accounts for the high field switching in amorphous grain boundary. Microscopic mobilities used for describing the carrier transport provides a physical basis for introducing the grain voltage across the unit cell of polysilicon. The voltage, in turn, distributes itself to preserve a constant current density therein. This new criterion yields a new voltage partitioning scheme, and a general expression for the corresponding current is derived in terms of pertinent system parameters.     

基于光电热理论的LED热阻测量方法

热阻是反映发光二极管(LED) 器件散热能力的综合参数。本文基于光-电-热(PET)理论,简化了热阻与光通量、电功率 之间的关系,提出了一种利用LED光电特性测量其 热阻的新方法。即利用 光效随结温的变化率 k e 、 热耗散系数 k h 、 散热器 的表面温度 T hs 和最大光通量对应的电功率 P d, 计算 得到 LED 热阻。对不同型号器件进行热阻测量,与标称热阻具有 很 好的一致性,证实了本文方法 的可行性和通用性。 该热阻测量方法简单,无需昂贵的热阻测量仪器,具有较强的工程应用价值。     

Theory of conduction in polysilicon: Drift-diffusion approach in crystalline-amorphous-crystalline semiconductor system—Part I: Small signal theory

A theory of conduction in polycrystalline silicon is presented. The present approach fundamentally differs from previous theories in its treatment of the grain boundary. This theory regards the grain boundary as amorphous semiconductor in equilibrium contact with crystalline grain. The model explains the electrical properties of polysilicon in terms of the electronic and structural parameters of the material and is in excellent agreement with the experimental data. The formulation is applicable for arbitrary grain size, temperature, doping concentration, and applied voltage. Specifically, the temperature dependence of resistivity is explained in terms of conduction channels inherent in the amorphous grain boundary. Also, this paper explicitly compares the previous emission theories with the present model in terms of voltage partition scheme and I - V predictions.     

Design theory and experiments for abrupt hemispherical P-N junction diodes

The gold-bonded germanium diode offers a practical example of a hemispherical p-n junction. In this discussion, a theory is given for the parameters of interest in design for such a junction; i.e., the breakdown voltage, forward current, and transient effects. It is shown that voltage breakdown differs from that for a planar junction due to the concentration of the field by the geometry, this effect leading to lower breakdown voltages. The forward current and reverse transient dependence on the radius of the junction, bulk properties, and the thickness of the semiconductor, are shown. The nature of the back contact to the semiconductor is also discussed. Since this is a design theory, rigor is sacrificed in some cases for simplicity. Despite this, comparison of the theoretical predictions with experimental results usually shows good agreement. The possibility of applying the results to other hemispherical geometries, such as point contact diodes, is considered briefly.     

Stability theory for thin Gunn diodes with dielectric surface loading

The critical nd product for the suppression of Gunn oscillations in transversely thin diodes has been derived as a function of the dielectric surface loading. For permittivities of the dielectric higher than about one and a half times that of the active medium, a saturation of (nd)crit towards the infinite-surface-loading value is found.     

A stimulated inelastic tunneling theory of negative differential resistance in metal-insulator-metal diodes

The negative differential resistance that has been observed in the current-voltage characteristics of some metal-insulator-metal (MIM) diodes is investigated theoretically. A refined theory, involving the stimulated inelastic tunneling of electrons through the diode's insulating layer, is developed to explain the negative resistance. Electrons can tunnel inelastically through the insulating layer by emitting surface plasmons. It is shown that if the diode structure forms a resonant cavity of the proper frequency and sufficiently highQ-factor, the effect of emitted plasmons can be contained long enough to stimulate additional inelastic tunneling. Second order perturbation theory is used to derive an equation for the current-voltage characteristic of an MIM diode exhibiting negative differential resistance. Numerical calculations show that aQ-factor of10^{2}-10^{4}is required to match the theoretical results to published current-voltage characteristics of MIM diodes with negative differential resistance.     

Improved theory for E-plane symmetrical tee junctions

L. Lewin's theory (1975), which describes an E-plane symmetrical tee junction by an equivalent circuit with only three parameters, is examined. It is shown that although the theory is formally correct, its circuit parameters depend on the amplitudes of reflected waves. An improved theory corrects this fault     

Large-signal theory for rectangular-voltage operation of a uniform avalanche zone in IMPATT diodes

Explicit solutions are derived for the currents in a lightly doped high-field zone of an IMPATT diode subject to constant E field avalanche. Resulting particle-current waveforms, diode impedances and r.f. powers are calculated for Si and GaAs with the avalanche period followed by a sudden transition to a low-voltage carrier-extraction period. It is concluded that the addition of a drift zone will only ease impedance matching and enhance efficiency when differences of either ionisation rates or drift velocities between electrons and holes exist.