Abstract The frequency of oscillations can be controlled by applying uniform illumination to at least one surface of photoconducting semiconductors which exhibit a negative differential conductivity and traveling regions of space charge. The method is particularly useful in Gunn effect devices utilizing gallium arsenide (GaAs), but applies also to other photoconducting semiconductors exhibiting the Gunn effect and also to piezoelectric semiconductors exhibiting traveling domains due to acoustoelectric interactions between acoustic waves and the charge carriers. Also described is a principle for reducing the fluctuations in the carrier density present in the crystalline semiconductor solid by reducing the inhomogeneities as a percentage of the total carrier density by uniformly illuminating the crystal. The reduction in the present fluctuations in the carrier density is of particular significance in gallium arsenide Gunn devices operating in the LSA mode.
A method of increasing the efficiency of a LSA oscillator-type device having microwave oscillations generated by a body portion of said device exhibiting negative differential conductivity and used in combination with a resonant circuit comprising the steps of applying a voltage to spaced electrodes across said body portion of a photoconducting semiconductor of a magnitude greater than a threshold value to initiate LSA oscillations, uniformly illuminating at least one portion of one surface of said body portion to a level sufficient to increase the carrier density in said portion to a value greater than 1012 divided by said electrode spacing, and maintaining said applied voltage at a value greater than a sustaining value.
Claim 2
Independent Claim
121 words
A method of increasing the efficiency of a LSA oscillator-type device having microwave oscillations generated by a body portion of said device exhibiting negative differential conductivity and used in combination with a resonant circuit comprising the steps of applying a voltage to spaced electrodes across said body portion of a photoconducting semiconductor of a magnitude greater than a threshold value to initiate LSA oscillations, uniformly illuminating at least one portion of one surface of said body portion to a level sufficient to vary the carrier density in said portion to a value sufficient to increase the efficiency of said portion and maintaining said illumination at said level while maintaining said applied voltage at a value greater than an oscillation sustaining value.