Showing papers on "Diffusion capacitance published in 1972"

A theoretical investigation on the generation current in silicon p-n junctions under reverse bias

Abstract: In a reverse-biased p-n junction, the current component arising from carrier generation in the depletion layer has been up to now considered proportional to the depletion layer width W. As the junction capacitance varies inversely with W, the current-capacitance product should be constant with the applied voltage whenever the reverse current is essentially a generation current. There is experimental evidence, however, that this is not so. In the present paper it is shown that an important cause of such a discrepancy is the considerable difference existing between the depletion layer width and the width Wi of the region in which the generation function reaches its maximum value. In fact, the generation current is proportional to Wi rather than to W and the current-capacitance product must be expected to vary as the ratio W i W , which is all but constant with the applied voltage. A simple model is proposed for evaluation of the generation current effective width Wi, which has been explicitly computed as a function of the applied reverse voltage and of the doping profile in cases of abrupt and linearly-graded junctions.

Charge coupled circuits

Abstract: Output circuit for charge coupled circuit includes an electrically floating diffusion at the substrate surface. The diffusion is coupled to a surface charge storage location and receives a surface charge signal therefrom. This diffusion may connect to a control electrode at the input circuit for a second charge coupled circuit for controlling the flow of surface charge from a source electrode to a second charge storage location. The diffusion periodically is reset by periodically forming a conduction channel between that diffusion and a drain electrode.

Determination of the spatial distribution of deep centers from capacitance measurements of pn junctions

Abstract: Effects of a spatial distribution of deep centers on the junction capacitance are reported for the first time. It is shown that the spatial distribution of deep centers can be calculated from capacitance data measured by both the capacitance‐voltage method and the Copeland method, if their energy level is known or assumed. The theory is examined with the experiment on silicon p+n junctions irradiated with 300‐kV protons. The analysis yields a value 0.40 eV below conduction band for the energy level of radiation‐induced defects, as well as a distribution of the defects with depth.

Electrical properties of CdSPbS heterojunctions

Abstract: Photovoltaic effects of CdSPbS heterojunction were measured for visible and near-i.r. regions. A marked photovoltaic response was observed extending to the wavelength of 3·3 μ and found to be fairly uniform in quantum efficiency. The detectivity was determined to be 3·4 × 10−11 W8 for NEP (noise equivalent power) and 1·5 × 1010 cm ( Hz ) 1 2 / W for D (detectivity) at 900 Hz. Electrical properties of the heterojunctions such as junction capacitance and current-voltage characteristics were measured and the energy band scheme of the heterojunction was constructed. The experimental values of barrier height obtained from different methods were in good agreement and they gave the value of approximately 0·3 eV. From the results the photovoltaic effect in the i.r. region was considered to be due to the photoemission of electrons from PbS to CdS.

Zener diode structure having three terminals

Abstract: The zener diode structure is fabricated by standard monolithic processes and provides a constant reference voltage for driving a high impedance load. The diode includes an anode element provided by P-type diffusion into an epitaxial layer. Electrical connections between the anode and the surface terminals of the device are provided by ''''base'''' diffusion. A cathode element is formed by an ''''emitter'''' diffusion which extends from the surface of the epitaxial layer, into the base diffusion, and borders the anode to form an anode-to-cathode junction. Since the base diffusion has a higher resistivity than the anode-to-cathode junction, buried breakdown occurs at the anode-to-cathode junction. The drive current for the zener is conducted by a path between a first anode terminal, which is connected to the base diffusion, and the cathode terminal. The constant reference voltage is developed between a second anode terminal, which is also connected to the base diffusion, and the cathode terminal.

Design considerations of step recovery diodes with the aid of numerical large-signal analysis

Abstract: Switching behavior of the step recovery diode (SRD) is studied through exact large-signal analysis Two numerical methods are presented One is suitable for steady-state and slow-transient calculations, while the other is based on a principle given by Scharfetter and Gummel, being appropriate for fast-transient calculation Criteria for each method are described in terms of space and time intervals A variety of doping profiles is generated by seven parameters, to determine the influence of each parameter on switching response The normally defined transition time for current falloff from 90 to 10 percent consists of a physical transition phase and the phase of the CR time constant, which is defined as the product of junction capacitance and series resistance The former is minimized by a narrow region of light doping, or by an abrupt profile, whereas the latter is minimized by a wide region of light doping, thus making a compromise necessary Under the assumption of improved device fabrication technology, operation with low external impedance will allow total transition time to decrease to about one-half or one-third of today's standard sample As was pointed out by Moll et al, a small amount of series inductance is desirable for fast transition

Metal-insulator-semiconductor structures having reduced junction capacitance and method of fabrication

Abstract: Metal-insulator-semiconductor structures characterized by reduced junction capacitance and methods of fabrication are disclosed. A substantially intrinsic region beneath the junction is formed by implanting selected ions. The ion implantation does not produce lateral diffusion of conventionally formed junctions, and therefore breakdown and packing density are not changed. The substantially intrinsic region does, however, increase the space charge region of the adjacent junction, thus reducing the effective capacitance. In the preferred method of fabrication, ions are implanted using the same mask employed in forming the p-n junction.

A fast algorithm for the calculation of junction capacitance and its application for impurity profile determination

Abstract: A fast algorithm is described which calculates the space charge layer width and junction capacitance for an arbitrary impurity profile and for plane, cylindrical and spherical junctions. The algorithm is based on the abrupt space charge edge (ASCE) approximation. A method to use the algorithm for the determination of impurity profiles for two-sided junctions is presented. An expression is derived for the built-in voltage to be used for capacitance calculations with the ASCE approximation. Experimental evidence is given that the algorithm permits very accurate capacitance calculations and also predicts the exact temperature dependence of the junction capacitance.

Effects of transverse diffusion and transverse stored charge in alloy transistor base

Abstract: Transverse diffusion of minority carriers under the action of a transverse concentration gradient in the base, which will exist even in the absence of surface recombination, is shown to make an appreciable contribution to the base current and is to be taken into account in considering transistor action. The dependence of transistor current gain on base geometry is traced to this factor. The role hitherto assigned exclusively to surface recombination in this regard and in several areas of disagreement between the predictions of the one-dimensional theory and experimental observations now appears to be largely assignable to transverse diffusion. Transverse diffusion processes in alloy junction type and grown junction type base geometries are contrasted. The adverse effect of transverse stored charge on the high frequency performance of transistors is analysed and their effect on increasing the ‘ effective base transit time ’ discussed. The possibility of localized reduction of volume lifetime in the base in...