Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. [40]-[42].

Thesis (M.S.)--University of Wisconsin--Madison, 1960. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 34-35).

Thesis (M.S.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 64).

Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. [85]-88.

The noise characteristics of ideal photovoltaic p-n junction diodes are discussed and investigated. The hypothesis is advanced that the open-circuit noise from an illuminated ideal diode is entirely due to the shot noise of the various current contributions. Theoretical justification for this theory is developed and the parameter t, the effective noise temperature ratio, is introduced. The possible reasons for excess noise in p-n photo-diodes observed in earlier experiments are suggested. The dc and ac behavior of a real diode chosen to be very nearly ideal in its dc characteristic is found to be consistent with existing diode theory. The various parameters appropriate to the device are evaluated. Equipment for noise measurement is selected and a comparison technique adopted. This method avoids many of the possible errors inherent in an absolute measurement and allows an equivalent noise resistance resolution of about 200 ohms at room temperature in the 200 cs bandwidth measured. The open-circuit noise of the selected diode is measured at 20 and 30 kc as a function of illumination and the results interpreted in terms of the equivalent resistance in thermal equilibrium which would give the same noise. Comparison of this set of values with the real part of the junction impedance in each case indicates that the theory advanced is adequate to predict noise under these circumstances. The signal-to-noise ratio for a photo-diode used as an open-circuit radiation detector is developed, and several recommendations are made regarding the design of a photo-diode to display the most favourable signal-to-noise ratio under illumination. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This work is concerned with a fundamental experimental study of the operation of Gunn effect diodes in microwave cavities. Diodes with different parameters were fabricated from single GaAs crystals. The diodes were tested in resistive circuits for measuring some of their characteristics and for assessing their performance. The effect of the ohmic contacts on the performance of the diodes was demonstrated. Determination of the carrier concentration and mobility for the GaAs crystal was made using the Hall effect and conductivity measurements. Microwave coaxial cavities were designed and built for the operation of the diodes. The cavities had wide tuning range and provided variable impedance at the diode by changing the coupling to the output line. The results obtained showed that the upper limit of the frequency of oscillation varied from about 1.8 f to 2.5 f as the nl product of the diode varied from 0.4 to 3x10¹² cm⁻². At frequencies smaller than the transit time frequency the operation was in two modes; one was the delayed domain mode at lower values of bias. The other was observed at higher bias and was considered to be amultiple domain mode in which the domain reaches the anode before the voltage swings below threshold, and a new domain forms and then gets quenched before a new cycle begins. For the delayed domain mode, a theory has been developed which was in fair agreement with the experimental results. It was found that the range of bias in which the diode could oscillate coherently decreased as both the frequency and the nl product were decreased. The results obtained in the LSA mode showed that the lower limit of oscillation decreased as the carrier concentration decreased, but increased when the bias increased. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

Graduation date: 1991

No description available.

Measurements have been made on a variety of germanium and silicon junction diodes in order to determine departures from the ideal behavior both under illuminated and dark conditions. The diodes included alloyed, grown and diffused junction types and the experimental study was largely confined to forward voltage. Carriers injected by a forward voltage into the bulk regions of a p-n junction in Ge or Si reduce the resistances of these regions, A model of a photodiode consisting of an ideal diode (Shockley, 1949) in series with this carrier modulated resistance produces good agreement with the experimentally observed dark chs.; in one Ge alloy diode the agreement was exact up to at least 0,7V forward voltage. For large forward currents (density of injected carriers comparable to injected carrier density) the Shockley expression relating I and V is no longer valid nor consequently is the conductivity modulation theory. This theory, making use of the experimental dark chs, and the experimental dynamic capacity measurements, is able to deduce many of the parameters of the diode material e.g. Ƭ𝞺, Pո,Ψo. The chs. of the diode dark and illuminated have been found to intersect at large forward currents. Theoretical investigation of the condition for crossover in various models of the diode is made. The physical meaning of this condition is that at some forward voltage the resistance of the diode is sufficiently reduced on illumination to offset the effect of the opposed internal photo-e.m.f.. For an ideal diode the relation between the short circuit photo-current and open-circuit photo-e.m.f. (photochs.) should simply be the same as the dark forward chs., except for a reversal of sign of the current. The fact that the experimental photochs falls below the ideal photochs is attributed to internal resistance in the diode and an expression is developed from this assumption; the theoretical expression is largely consistent with experiment. Several other models are examined for the non-ideal behavior of junction diodes which attempt to take into account the possible effects of the resistance of the bulk material and of the electrode-semiconductor contact; the implications of non-linear recombination are also investgated. It is found that none of these alternative models is as successful as the conductivity-modulation scheme in explaining the dark, the illuminated and the photocharacteristics. / Science, Faculty of / Physics and Astronomy, Department of / Graduate