Cooled, extrinsic GE that is voltage biased to produce a spontaneous current oscillation exhibits frequency locking, quasiperiodicity, and chaos when driven with a sinusoidal voltage. The low-frequency current power spectrum at the transition from quasiperiodic to chaotic behavior agrees in detail, both in frequency and in amplitude, with the calculated universal spectrum of the circle map. The large dynamic range (> 70 dB) and the convenient frequency (10 kHz) of the spontaneous oscillation make this an excellent system for testing the predictions of theory.

• Received 16 June 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.1060