Final answer:
A semiconductor diode enables half-wave rectification by allowing current to flow only during the positive half-cycles of AC and blocking it during negative half-cycles, thus converting AC to pulsating DC.
Step-by-step explanation:
A semiconductor diode is essential for half-wave rectification, which involves the conversion of alternating current (AC) into direct current (DC). When AC is applied to the diode, it allows current to flow through only during the positive half-cycles, as the diode is forward biased in this condition, enabling electrons to pass the p-n junction. During the negative half-cycles, the diode is reverse biased, preventing current from flowing as the depletion layer is widened. Thus, the output is a DC that pulsates with each positive half-cycle of the AC input. This half-wave rectification is a fundamental building block in power supplies and electronic devices that require DC.