Define following terms. i. Critical Temperature ii. Persistent Current iii. Isotope effect
[3 marks]Explain hot point probe method with necessary diagrams.
[4 marks]Explain in detail how Kronig and Penney model explains the origin of band gap in semiconductors.
[7 marks]Compare n-Type and p-Type Semiconductors.
[3 marks]Distinguish between Type-Iand Type-II Superconductivity.
[4 marks]Determine the necessary formula for density of hole in Valence Band for Intrinsic Semiconductors.
[7 marks]What are Einstein’s coefficients? Give relation between them and discuss the result.
[7 marks]Define: i. Energy Gap ii. Fermi Function iii. Density of states
[3 marks]Estimate the position of Fermi Level at 300 Kfor a material with E = C 0.8 eV and E = 0.5 eV (m * = 0.14m and m * = 0.28m , m is rest Ve 0 h 0 0 mass of an electron).
[4 marks]Illustrate Four probe method for thin sheet and bulk sample in detail.
[7 marks]What are the postulates for free electron theory?
[3 marks]In an intrinsic semiconductor, energy gap is 1.3 eV. Evaluate the ratio between its conductivity at temperature 700 Kand 400 K.
[4 marks]Show that Junction capacitance is inversely proportional to square root of Reverse biasing Voltage.
[7 marks]What do you mean by Photo Voltaic Effect? Write its three applications in the field of engineering.
[3 marks]Using Fermi function, evaluate the temperature at which there is 20 % probability that an electron in solid will have energy 0.3 eV above Eof F eV.1
[3 marks]Explain at least seven properties of Superconductors in detail with necessary diagram and equations.
[7 marks]Define : i. Population Inversion ii. Meta stable state iii. Active Medium
[3 marks]Explain how the materials are classified into conductors, semiconductors and insulators with the help of energy band diagrams.
[4 marks]Briefly outline the mechanism of superconductivity using BCS theory and explain penetration depth.
[7 marks]Compare Direct Band Gap semiconductors and Indirect Band Gap semiconductors
[3 marks]What are Excitons? explain the types of Exciton.
[4 marks](i) Estimate the concentration of holes and electrons in n-type silicon at 300 K. If the conductivity is 8 X 104 Ʊ/m. also find these value for p- type Si. n = 2.5 X 1016 m-3 electron and hole mobility is 1600X10-4 i , m2/V.Sec and 700X10-4 m2/V.Sec respectively. (ii) Evaluate the Electron and Hole concentration at room temperature, for a intrinsic semiconductor, if its conductivity at room temperature is 8×10- 4 Ʊ/m. The mobility of Electron and Hole are 0.24 m2/V.Sec and 0.08 m2/V.Sec respectively.
[3 marks]List difference between drift and diffusion current
[3 marks]Explain in detail the Fermi’s Golden Rule.
[4 marks](i)In a solid consider an energy level lying 0.2 eV above Fermi level. Estimate the probability of this level not being occupied by an electron at room temperature. (ii)Arectangular semiconductor specimen of thickness 1 mm is placed in the magnetic field of flux density 0.5 Wb/m2. Current of 1.5 mA is flowing through the specimen in one direction. Evaluate Hall coefficient of the material if generated hall voltage is 7.5 mV.
