Semiconductor Fundamentals Unit 2 – Diodes and Half-Wave Rectification
Similarly, the positive charges in the P type material of the anode are attracted toward the
junction by the increased negative charge across the barrier.
When the applied voltage overcomes the barrier voltage, the depletion region width is reduced,
and electrons move across the junction toward the positive terminal of the voltage source. As
long as the applied voltage exceeds the barrier voltage, electron flow continues and the diode is
fully forward biased, or in the on state.
When a positive voltage is applied to the cathode and a negative voltage to the anode, electrons
in the N type material are attracted away from the junction toward the voltage source positive
terminal. Positive charges in the P type material are also attracted away from the junction toward
the negative terminal of the voltage source. These charge movements increase the width of the
depletion region, causing the diode to be reverse biased (in its off state) with almost no current
flow.