Avalanche breakdown region:

Even though these regions are well described for sufficiently large applied voltage, they overlap somewhat for small (less than a few hundred milli volts) biases. For instance, in the typical grounded-emitter configuration of an NPN BJT employed as a pull down switch in digital logic, the "off" state never includes a reverse-biased junction since the base voltage never goes below ground; yet the forward bias is close enough to zero that necessarily no current flows, so this type of end of the forward active region can be considered as the cutoff region.