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The studies of avalanche noise reported by Haitz are extended to frequencies up to and above the avalanche frequency ωa. It is found that the open-circuit spectral voltage density is flat within ±5% from less than 100 Hz up to frequencies approaching ωa. Near ωa the open-circuit spectral voltage density increases with frequency, goes through a maximum at ωa and then decreases rapidly. The spectral power density is similarly flat but fails to exhibit an expected maximum at ωa. For ω≫ωa the spectral power density decreases with ω−4. The experimental results are in good agreement with Hines' theory of avalanche noise for ω≪ωa and ω≫ωa. The discrepancies observed near ωa are thought to be caused by an oversimplification in Hines' theory which neglects internal diode losses. Compared with conventional noise sources such as temperature-limited diodes or gas discharge tubes, avalanche diodes have several advantages: larger noise output, larger bandwidth, lower 1/f noise, low power consumption, small size, and low weight.

This Letter reports avalanche noise studies on microplasma-free guard-ring avalanche diodes. The low and high frequency approximations of Hines' theory are compared with experimental results at 1 kHz and 3 to 9 GHz, respectively. Good agreement is found between experiment and theory at both low and high frequencies. The open-circuit spectral voltage density is white up to the avalanche frequency ωa and decreases inversely with current. For ω ≫ ωa the spectral noise power density falls off with ω4.

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