Harmonics produced by the nodinearity in the current-voltage characteristics of a ballistic diode are studied for a GaAs sample of thickness 1 μm at 77 K under collision-free condition. Harmonic generation is found to be maximum at zero bias, the value for the second- harmonic current being 50 percent for a signal amplitude of 0.2 V. Copyright © 1983 by The Institute of Electrical and Electronics Engineers, Inc.