Why diode acts as insulator in reverse biasing?

a diode has two junctions one is doped with p-type and another is doped with n-type.a diode connected in reverse bias means that the n-channel is connected to the positive end of the battery and p-channel is attached to the negative end of the battery

if we start increasing the reverse voltage the width of depletion region increases and the exchange of charge carriers (holes and electrons) is inhibited so we expect zero current in the circuit but on experimental observations we had confirmed that a small current (micro-amp) is observed due to the minority charge carriers(electrons in p-channel and holes in n-channel) present in the diode , for these minority charge carriers the applied voltage appers as as forward bias to them so they conduct .

but on further increasing the reverse voltage we note a large change in the reverse current this is due to junction breakdown (the depletion region is broken , so there is no demarcation between p-channel and n-channel in the diode). the voltage at which this phenomena occurs is called 'break-down voltage'