ʜᴏᴡ ᴅᴏᴇs ᴛʜᴇ ᴅᴇᴘʟᴇᴛɪᴏɴ ʀᴇɢɪᴏɴ ᴏғ ᴀ ᴘ-ɴ ᴊᴜɴᴄᴛɪᴏɴ ᴅɪᴏᴅᴇ ɢᴇᴛ ᴀғғᴇᴄᴛᴇᴅ ᴜɴᴅᴇʀ ʀᴇᴠᴇʀsᴇ ʙɪᴀs?
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Answer:
When a junction diode is Reverse Biased the thickness of the depletion region increases and the diode acts like an open circuit blocking any current flow, (only a very small leakage current will flow).
A PN Junction Diode is one of the simplest semiconductor devices around, and which has the characteristic of passing current in only one direction only. However, unlike a resistor, a diode does not behave linearly with respect to the applied voltage as the diode has an exponential current-voltage ( I-V ) relationship and therefore we can not described its operation by simply using an equation such as Ohm’s law.If a suitable positive voltage (forward bias) is applied between the two ends of the PN junction, it can supply free electrons and holes with the extra energy they require to cross the junction as the width of the depletion layer around the PN junction is decreased.By applying a negative voltage (reverse bias) results in the free charges being pulled away from the junction resulting in the depletion layer width being increased. This has the effect of increasing or decreasing the effective resistance of the junction itself allowing or blocking the flow of current through the diodes pn-junction.Then the depletion layer widens with an increase in the application of a reverse voltage and narrows with an increase in the application of a forward voltage. This is due to the differences in the electrical properties on the two sides of the PN junction resulting in physical changes taking place. One of the results produces rectification as seen in the PN junction diodes static I-V (current-voltage) characteristics. Rectification is shown by an asymmetrical current flow when the polarity of bias voltage is altered as shown below.