Semiconductor Devices Questions and Answers for Viva

Answer-1: A “semiconductor" is a substance with characteristics intermediate between those of a "conductor" that conducts electricity like metal and an "insulator" through which electricity hardly flows. The ease with which electricity flows is related to the magnitude of the substance’s electrical resistance. If the electrical resistance is high, the current hardly flows, and if the electrical resistance is low, the electric current flows easily.

Answer-2: Silicon (Si) and germanium (Ge) are well-known semiconductor materials. When they are pure crystals, these substances are close to insulators (intrinsic semiconductors), but doping a small amount of dopant causes the electrical resistance to drop greatly, turning them into conductors.

Answer-3: Depending on the kind of dopant, n-type or p-type semiconductor can be made.

Answer-4: Many kinds of semiconductor devices have been developed in line with the expansion of application fields and the progress of electronic equipment. “Discrete semiconductors” are single devices with a single function, such as transistors and diodes. “Integrated circuits (ICs)” are devices with multiple functional elements mounted on one chip. Typical ICs include memories, microprocessors (MPUs), and logic ICs

Answer-5: It is an intrinsic semiconductor doped with phosphorus (P), arsenic (As), etc. An electron derived from the bound electrons of phosphorus can be made free (free electron) by adding a small amount of phosphorus to pure silicon crystal. Movement of the free electrons pulled to “+” electrode makes current flow.

Answer-6: It is an intrinsic semiconductor doped with boron (B), indium (In), etc. Where silicon and boron are bonded, lack of an electron can be brought about by adding a small amount of boron to pure silicon. This lack is called a hole. When voltage is applied in this situation, an adjacent electron moves to this hole and the place the electron is removed from becomes a new hole. Holes move to "–" electrode in sequence.

Answer-7: When P-type and N-type come into contact, carriers, which are holes and free electrons, are attracted to each other, recombine at the junction of P-type and N-type, and disappear.

Answer-8: A diode allows current to flow in only one direction while blocking it in the opposite direction.

Answer-9: The two terminals of a diode are called the anode and the cathode.

Answer-10: A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power.

Answer-11: The two main types of transistors are bipolar junction transistors (BJTs) and field-effect transistors (FETs).

Answer-12: In an NPN transistor, current flows from the emitter to the collector through a layer of P-type semiconductor, while in a PNP transistor, current flows from the emitter to the collector through a layer of N-type semiconductor.

Answer-13: A field-effect transistor is used to control the flow of current using an electric field applied to the semiconductor material.

Answer-14: A rectifier diode is used to convert alternating current (AC) into direct current (DC) by allowing current to flow in only one direction.

Answer-15: A Zener diode is designed to operate in the reverse-biased breakdown region, allowing it to maintain a nearly constant voltage across its terminals when it is conducting in reverse-biased mode, unlike a regular diode which would be damaged in such conditions.

Answer-16: A Schottky diode is a special type of diode with a low forward voltage drop and fast switching characteristics, often used in high-frequency applications.

Answer-17: An LED emits light when current flows through it, converting electrical energy into light energy.

Answer-18: A photodiode is a semiconductor device that converts light into electrical current, commonly used in light sensors and optical communication systems.

Answer-19: A thyristor is a four-layer semiconductor device used for controlling large amounts of electrical power, often employed in power control and switching applications.