Tunnel diodes for low noise amplification

The noise generated by tunnel diodes in amplifier circuits is directly proportional to the product of the negative resistance and current at the operating point in the negative resistance portion of the I-V characteristic. In this paper, the factors influencing the negative resistance-current product, referred to as the shot noise constant K, will be discussed. Design factors that can be introduced to minimize K, and limitations thereof, will be reviewed. Experimental results on germanium tunnel diodes designed for low noise amplification will be presented to show the correlation of experimental measurements with the theoretical background discussed previously. A new approach to the problem of obtaining low noise constant diodes will then be presented. This includes: a) Reasons for the selection of gallium antimonide as a choice semiconductor material for low noise tunnel diodes. b) A review of the metallurgy of this material and a general description of GaSb tunnel diode fabrication technology, c) A summary of results achieved to date showing the superiority of GaSb tunnel diodes over germanium units for low noise amplifier applications.