Budapest University of Technology and Economics, Faculty of Electrical Engineering and Informatics

Electronics, Microelectronics, Solid States, Semiconductors

To give a survay about the physics of semiconductor materials and devices., deepening of the previous knowledge connected to semiconductors. The bases obtained in this subject helps the understanding and attainment of other Ph.D. subjects connected to semiconductor devices. It especially helps the understanding of devices with extreme low dimensions as well as the understanding of nanoelectronic, nanomechanic and sensor devices. 

1. Electrons in solid states. Density of states, occupation of states. Basic lattice structures. Reciprocal lattice. Surfaces and interfaces. Scattering mechanisms. Elektrons in the periodic potencial space.

2. Semiconductor band structures. Band structures of heterojunctions, quantum wells and super lattices. Changing of the band structure under mechanical stress.

3. Doping of semiconductors, highly doped semiconductors. Vibration of the lattice, phonons, phonon statistics, phonons in heterojunctions. Transport phenomena, Boltzmann equation. Scattering on crystal defects, on doping atoms and charge carriers.

4. Velocity-fieldstrength relations, transport of charge carriers. Ballistic transport at very small dimensions. Phenomenon of overshooting. Transport phenomena in heterojunctions, in quantum structures and superlattices. Generation, direct and indirect rekombination. Tunnel effect, tunnal current. Interaction of semiconductors and phonons. Intraband and interband transitions. Semiconductors in magnetic field. Lattice defects. 

 5. The pn junction. Band diagram.. Depleted layer and capacity at different doping profiles. Current-Voltage characteristics. Secondary effects in forward direction. Rekombination current in the depletion layer. Series resistance and its modulation. High-level injection. Current crowding. Ideality factor. Secondary effects under reverse bias.  Generation current in the depletion layer. Avalanche breakdown, avalanche voltage. The effect of curvature on the breakdown voltage.

6. Thermal resistance, thermal runaway. Small-signal circuit diagram, the frequency dependence of the small-signal admittance.  Switching behaviour of the pn junction. Switching times and factors influencing them.

7.The PIN diode. Structure, behaviour in forward and reverse directions, breakdown voltage, small-signal admittance, cut-off frequency. Metal-semiconductor junction. Schotttky diode. Structure, currents, properties. Ohmic metal-semiconductor junctions. N-n type heterojunction as high-speed switch. Bulk-barrier diode.

8. The  bipolar transistor. Structure, basic operation, characteristics. Dependence of the current amplification factor upon the operating point, recombination current, high-level injection. Current crowding. Breakdown voltages. Punch-through voltage. Optimization of homogeneous and inhomogeneous base transistors.

9. Small-signal behaviour and circuit diagrams. Cut-off frequencies and their dependence upon the structure of the device. Possibilities for increasing of the cut-off frequencies by optimal constructions.  Switching properties of the bipolar transistor. Determination of the switching times.

10. The heterojunction bipolar transistor (HBT). The effect of the emitter.base heterijunction upon the emitter efficiency. Optimization possibilities to increase the cut-off frequencies.  Different types of HBT-s. Compound semiconductor, SiGe HBT,  polisilicon-emitter transistor.

 11. Tyristors. Structures, operation, characteristics, parameters. Dependence of the current amplification factor upon the current and its effect upon the I-V chaacteristics.. The problem of dU/dt and dI/dt. Transient processes.

 12. The MOS structure. Accumulation, depletion, inversion, deep depletion. Relation between the surface field strength and surface potential. Threshold voltage. Dependence of the  MOS capacitance upon the operating point and the frequency. Capacity transient. Structure and operation of the MOS FET. Current-voltage characteristics and its regions.

Lecture 

a.      In term time: 1 test with at least passed level.

b.      In exam periode passing the exam (written).

c.              Pre-exam: yes

In the last education week there is a possibility for one substitutional test. 

Continuously on registration. 

S.M. Sze:Physics of Semiconductor Devices. Wiley&Sons, 1981

J. Singh: Physics of Semiconductors and their Heterostructures. Mc Graw-Hill, Inc 1993. ISBN 0-07-057607-6