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  • Semiconductor Electronics: Materials, Devices and Simple Circuits

    Prof. G. Vijayendra SBM Jain College, V.V Puram

    © G. Vijayendra, Prof. in Physics

    Prof. G. Vijayendra SBM Jain College, V.V Puram

    PHYSICS

  • Semiconductors have ρ higher than that of metals and have negative α i.e., their resistivity decreases with increase in temperature.

    Synopsis

    © G. Vijayendra, Prof. in Physics

    Semiconductors have ρ higher than that of metals and have negative α i.e., their resistivity decreases with increase in temperature.

  • CLASSIFICATION OF SEMICONDUCTORS ON THE BASIS OF THE COMPOSITION

    SEMICONDUCTORSSEMICONDUCTORS

    Elemental semiconductor

    Si Ge

    Elemental semiconductor

    Si Ge

    Compound Semiconductor

    Compound Semiconductor

    © G. Vijayendra, Prof. in Physics

    Elemental semiconductor

    Si Ge

    Elemental semiconductor

    Si Ge

    Compound Semiconductor

    Compound Semiconductor

    Inorganic CdS, GaAs, CdSe, InP

    Inorganic CdS, GaAs, CdSe, InP

    Organic anthracene polypyrrole polyaniline

    Organic anthracene polypyrrole polyaniline

  • Metals:

    © G. Vijayendra, Prof. in Physics

  • Insulators:

    © G. Vijayendra, Prof. in Physics

  • Semiconductors:

    © G. Vijayendra, Prof. in Physics

  • SemiconductorsSemiconductors

    Intrinsic semiconductor

    Intrinsic semiconductor

    Extrinsic Semiconductor

    Extrinsic Semiconductor

    © G. Vijayendra, Prof. in Physics

    Intrinsic semiconductor

    Intrinsic semiconductor

    Extrinsic Semiconductor

    Extrinsic Semiconductor

    n–type semiconductor

    n–type semiconductor

    p–type semiconductor

    p–type semiconductor

  • Energy band diagrams of intrinsic semiconductors

    © G. Vijayendra, Prof. in Physics

    T = 0 K T > 0 K

  • N-type semiconductor

    This is obtained by doping pure semiconductors like Si or Ge with a pentavalent dopant like phosphorus.

    © G. Vijayendra, Prof. in Physics

  • P–type semiconductor This is obtained by doping pure semiconductors like Ge or Si with a trivalent impurity like aluminium.

    © G. Vijayendra, Prof. in Physics

  • p-n junction under forward bias

    © G. Vijayendra, Prof. in Physics

  • p-n junction under reverse bias

    © G. Vijayendra, Prof. in Physics

  • The dynamic resistance rd of a diode is defined as the ratio of small change in voltage (V) to the corresponding change in current (I)

    ..............d V

    r I

       

    © G. Vijayendra, Prof. in Physics

    ..............d V

    r I

       

  • Rectification

    Half wave rectifier (HWR)

    © G. Vijayendra, Prof. in Physics

  • Full wave rectifier (FWR)

    © G. Vijayendra, Prof. in Physics

  • Zener diode

    © G. Vijayendra, Prof. in Physics

    I-V characteristics Reverse bias

  • OPTOELECTRONIC JUNCTION DEVICES

    Optoelectronics is the study and application of electronic devices that source, detect and control light. Some of the optoelectronic devices are photodiodes, light emitting diodes and solar cells (photovoltaic cells).

    © G. Vijayendra, Prof. in Physics

    OPTOELECTRONIC JUNCTION DEVICES

    Optoelectronics is the study and application of electronic devices that source, detect and control light. Some of the optoelectronic devices are photodiodes, light emitting diodes and solar cells (photovoltaic cells).

  • Photodiode

    © G. Vijayendra, Prof. in Physics

  • LIGHT EMITTING DIODE (LED) LED is a heavily doped p-n junction which under forward bias emits spontaneous radiation.

    © G. Vijayendra, Prof. in Physics

  • Solar Cell (photo voltaic cell) A solar cell is basically a p-n junction which generates emf when solar radiation falls on the p-n junction.

    © G. Vijayendra, Prof. in Physics

  • TRANSISTOR It has three doped regions namely emitter, base and collector.

    © G. Vijayendra, Prof. in Physics

    Emitter: It is moderate in size and heavily doped. It supplies large number of majority charge carriers. Collector: It is larger in size compared to emitter and is moderately doped. Base: It is the Central region which is very thin and lightly doped.

  • Transistor as a switch and amplifier

    © G. Vijayendra, Prof. in Physics

  • Transistor as an oscillator An oscillator is an electronic device which produces sustained electrical oscillations (ac signal) of constant frequency and amplitude without any external input.

    Principle of a transistor oscillator An oscillator may be regarded as a self-sustained transistor amplifier with a positive feedback. (In-phase feedback).

    © G. Vijayendra, Prof. in Physics

    Transistor as an oscillator An oscillator is an electronic device which produces sustained electrical oscillations (ac signal) of constant frequency and amplitude without any external input.

    Principle of a transistor oscillator An oscillator may be regarded as a self-sustained transistor amplifier with a positive feedback. (In-phase feedback).

  • OR gate

    Truth Table: OR gate

    © G. Vijayendra, Prof. in Physics

    Truth Table: OR gate A B y=A+B 0 0 0 0 1 1 1 0 1 1 1 1

  • AND gate:

    Truth Table: AND gate

    © G. Vijayendra, Prof. in Physics

    Truth Table: AND gate A B y=A.B 0 0 0 0 1 0 1 0 0

    1 1 1

  • NOT gate

    Truth Table: NOT gate

    © G. Vijayendra, Prof. in Physics

    Truth Table: NOT gate

    A y=Ᾱ

    0 1

    1 0

  • NOR gate:

    Truth Table: NOR gate

    © G. Vijayendra, Prof. in Physics

    Truth Table: NOR gate A B 0 0 1 0 1 0 1 0 0 1 1 0

    y A B 

  • NAND gate:

    Truth table: NAND gate

    © G. Vijayendra, Prof. in Physics

    Truth table: NAND gate A B 0 0 1 0 1 1 1 0 1 1 1 0

    .y A B

  • 1. Electrical conductivity in a semiconductor is due to 1. electrons only 2. free electrons and ion cores. 3. free electrons and holes 4. ion cores and holes

    © G. Vijayendra, Prof. in Physics

    Answer: 3 both free electrons and holes are charge carriers

  • © G. Vijayendra, Prof. in Physics

    Answer: 1 intrinsically generated carriers are e-h pairs. Hence their numbers are equal.

  • 3. The movement of a hole is brought about by 1. the vacancy being filled by a free electron. 2. the vacancy being filled by a valence electron from a

    neighbouring atom 3. the movement of an atomic core 4. the movement of a free electron in the valence band

    © G. Vijayendra, Prof. in Physics

    3. The movement of a hole is brought about by 1. the vacancy being filled by a free electron. 2. the vacancy being filled by a valence electron from a

    neighbouring atom 3. the movement of an atomic core 4. the movement of a free electron in the valence band

    Answer: 2 hole moves opposite to the direction of electron motion.

  • 4. A p-type semiconductor is 1. positively charged 2. negatively charged 3. electrically neutral 4. an insulator at room temperature

    © G. Vijayendra, Prof. in Physics

    Answer: 3 Any extrinsic semiconductor is electrically neutral because while doping, only atoms are added.

  • 5. The ratio of the number of host atoms to that of impurity atoms in a doped semiconductor can be 1. 1 : 106

    2. 106 : 1 3. 103 : 1 4. 1 : 108

    © G. Vijayendra, Prof. in Physics

    5. The ratio of the number of host atoms to that of impurity atoms in a doped semiconductor can be 1. 1 : 106

    2. 106 : 1 3. 103 : 1 4. 1 : 108

    Answer: 2 106 : 1

  • 6. An n-type and a p-type semiconductor can be obtained by doping pure silicon respectively with 1. arsenic and phosphorus 2. indium and aluminium 3. phosphorus and indium 4. aluminium and boron

    © G. Vijayendra, Prof. in Physics

    6. An n-type and a p-type semiconductor can be obtained by doping pure silicon respectively with 1. arsenic and phosphorus 2. indium and aluminium 3. phosphorus and indium 4. aluminium and boron

    Answer: 3 n-type is obtained by doping Si with pentavalent impurity. p-type is obtained by doping Si with trivalent impurity.

  • 7. A piece of copper and a piece of germanium at room temperature are cooled to 90K. The resistance of 1. both will increase 2. both will decrease 3. copper increases while that of germanium decreases 4. copper decreases while that of germanium increases.

    © G. Vijayendra, Prof. in Physics

    7. A piece of copper and a piece of germanium at room temperature are cooled to 90K. The resistance of 1. both will increase 2. both will decrease 3. copper increases while that of germanium decreases 4. copper decreases while that of germanium increases.

  • 8. Identify the incorrect statement 1. The forbidden gap in case of silicon is 1.12eV 2. The energy gap in germanium is 0.72eV 3. The conductivity of silicon will be more than that of

    germanium at room temperature 4. When silicon is doped with