Usually, a Zener or avalanche breakdown region for a suitably doped P-N junction is used for voltage regulation as a substantial variation in the current (due to minority carriers) requires a negligibly slight variation in reverse bias voltage.
From the I-V characteristics of a P-N junction, it appears that when the forward bias voltage is much greater than the knee voltage, a significant variation in forward current also corresponds to a very slight variation in the forward voltage. Even if this knee voltage is very small compared to the reverse breakdown voltage, for small voltage ranges, a P-N junction in forward biasing should work as a voltage regulator.
Can a P-N junction diode be used as a voltage regulator in forward biasing for smaller voltage ranges?