ideal diode wth a positive voltage?
A very basic model of a diode says that no matter how much current is going through it in the forward direction, the voltage is 0. So the voltage can never be greater than 0 because that would require a "more than infinite" amount of current, which can't be produced by any source.

A more accurate model for a pn-junction diode is given by the Shockley diode equation

$$I = I_s \left(e^{\frac{qV}{nk_BT}}-1\right)$$

With this model you can predict the behavior for positive forward voltages, however if the voltage exceeds what we usually take as the turn-on voltage of the diode (often around 0.7 V), we will find that a very large current is produced (10's, 100's, 100's of A, or more). In the real world, forcing a high enough voltage will lead to burning out the diode.