The effect of an electric-field gradient on avalanche noise

The effect of an electric-field gradient on the excess avalanche noise is examined using both a Monte Carlo model and experiment. Nonlocal effects cause the noise to be significantly reduced as the electric-field gradient increases in a p+–n junction. For equal electron and hole ionization coefficients, lower noise is always achieved when carriers are injected into the high field end of these structures. Furthermore, for a constant noise figure and depletion thickness, a higher gain is always achieved in a p+–n junction compared a p+–i–n+. The results are explained in terms of coherence in ionization events.