Nonuniformly Doped Semiconductors Research Articles

Depletion layer and contact capacitance in non-uniformly doped semiconductors

We consider the dependence of the capacitance C of the semiconductor depletion layer versus the contact bias V. When the concentration of doping impurities varies in the plane parallel to the contact, we show that the standard Schottky dependence C−2(V) is no longer a straight line. We compute the effective concentration Neff from the slope of the dependence C−2(V) by using the perturbation and variation methods and compare Neff with previous theoretical and experimental data.

Simplified analytical quasi-transparent solution for minority carrier transport in non-uniformly doped quasi-neutral semiconductor regions

A simple analytical solution, which retains a general dependence of transport parameters on impurity concentration, is presented for minority carrier transport in nonuniformly doped semiconductor quasineutral regions. The new solution exhibits improved accuracy for high surface recombination velocities over all previous solutions of the same degree of analytic complexity which retain a general dependence of the transport parameters on impurity concentration, while retaining the same degree of accuracy for low surface recombination velocities as the most accurate of these previous solutions. The proposed solution exhibits accuracy comparable to significantly more complex third order expressions which are derived by three iterations using a systematic approach.

Comment on modeling of minority-carrier transport in nonuniformly doped silicon regions with asymptotic expansions [with reply

The most important result of a recent paper by Rinaldi [see ibid., vol. 40, p. 2307-17, 1993] was the development of a new, more accurate solution for the saturation current corresponding to a nonuniformly doped semiconductor region. Such a claim of novelty is unacceptable, since the same solution had been published earlier. This comment criticizes the liberal use of the word new in the original paper, as well as the methodology followed to derive the solutions. The Appendix suggests, however, a valuable mathematical transformation that permits a factor seven reduction of the computation time of the saturation current. A reply to the comments is appended. >

Influence of a non-uniformly doped semiconductor region on skin effect resistance of ohmic contacts in mm-wave IMPATTs

Skin effect resistance (SER) of metal- p + and metal- n + type ohmic contacts in mm-wave IMPATTs has been studied here in detail using an exact solution of the electromagnetic field equations and a multiple uniform layer approximation for the doping profile in the semiconductor. Representative profiles considered are for conventional diffusion and ion implantation. A special case of shallow As doping, resulting from implanted predeposition followed by drive-in diffusion, has also been considered for metal- n + (diffused) type contacts. It can be seen that p + and n +-regions formed by diffusion or ion implantation, with higher peak concentrations and steeper profiles, give lower skin effect resistance.

Surface-depletion effect correction to nonuniform carrier distributions by Hall measurements

Significant errors in the determination of carrier profiles obtained by the Hall-effect method result if the depletion effect at a semiconductor surface is not taken into account. A practical procedure for correcting the apparent measured carrier profiles for this surface-depletion effect is described for nonuniformly doped semiconductors. This correction method is then applied to Si-implanted GaAs and the results are compared with those of capacitance-voltage measurements. The number of total trapped charges in free-surface states are estimated to be about 1×1012 cm−2.

Theory ofC-U profiling of a nonuniformly doped semiconductor

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Comments on "Depletion approximation analysis of the differential capacitance-voltage characteristics of an MOS structure with nonuniformly doped semiconductors"

Comments on "Depletion approximation analysis of the differential capacitance-voltage characteristics of an MOS structure with nonuniformly doped semiconductors"

Surface depletion and inversion in semiconductors with arbitrary dopant profiles

A general analytical description of the depletion-layer problem in nonuniformly doped semiconductors is a valuable tool because it permits analytical manipulation of critical quantities for the purpose of establishing criteria and relating measurable quantities. A formulation is presented here which retains the dopant profile as an arbitrary function and defines integrals over this profile together with functions of the potential that uniquely specify the problem. An example of a such a criterion, which is presented, is the threshold voltage of a metal-oxide semiconductor field-effect transistor with a highly nonuniform substrate dopant profile.

An improved definition for the onset of heavy inversion in an MOS structure with nonuniformly doped semiconductors

The criterion for the onset of heavy inversion in an MOS structure with nonuniformly doped semiconductors on the basis of an appropriate definition has been derived. The present theoretical model is based upon the improved depletion approximation presented previously by one of authors [ 1]. The validity of the present criterion is confirmed compared with the results obtained from the present model and those obtained from the numerical solutions by assuming appropriate impurity distributions as a test sample. The results obtained from the present model are in excellent agreement with the numerically computed results.

Depletion approximation analysis of the differential capacitance—Voltage characteristics of an MOS structure with nonuniformly doped semiconductors

The semiconductor equations relating the differential capacitance-voltage characteristics of an MOS structure with nonuniformly doped semiconductors have been derived by using the depletion approximation based on the rigorous definition of the depletion layer width. The relationship between the depletion layer width and the differential capacitance is shown to be the same as the one derived using classical model that is sometimes taken for granted. At the same time, it is shown that the differential capacitance arises from the introduction (or removal) of majority carriers from the abrupt space-charge edge. Expressions derived using this model that are necessary to obtain the impurity distributions are the same as those developed by Kennedy et al. The present model will permit the explicit analysis of subthreshold characteristics in ion-implanted MOSFET's even for non-space-charge neutral profiles.

One-dimensional study of buried-channel charge-coupled devices

An analysis leading to some basic relations is performed on a one-dimensional model of a buried-channel charge-coupled device (CCD). Expressions for the charge distribution, potential, channel thickness, and location are obtained. These enable the effects of varying the device structural parameters, as well as the gate voltage and signal charge, to be examined very simply. The maximum charge-carrying capacity is discussed and compared to that for a surface-type CCD. Furthermore, the analysis is extended to a device with a nonuniformly doped semiconductor layer.

Lumped modeling of optical generation in nonuniformly doped semiconductors

When carrier density is normalized and recombination neglected, a single transport element accounts for both drift and diffusion. Optical generation is modeled by discrete current sources, and expressions for lumped elements are obtained in terms of integrals of the doping profile. Good physical intuition with respect to the effect of the profile on photocurrent transport is obtained, and analytical calculation of device quantum efficiency is facilitated.