


Politecnico di Torino  
Academic Year 2010/11  
05APMNX, 05APMOD Electronic devices 

1st degree and Bachelorlevel of the Bologna process in Electronic Engineering  Torino 1st degree and Bachelorlevel of the Bologna process in Physical Engineering  Torino 





Subject fundamentals
The course is mandatory for the Laurea degrees in Electronic Engineering and Physical Engineering, and it is the first element of the chain that, starting from solidstate physics, leads the student to understand both analogue and digital complex circuits. In particular, the competences acquired in Electronic Devices will be directly applied at both the theoretical and experimental levels in the Electronic Circuits course.

Expected learning outcomes
Detailed knowledge of the main electronic properties of solids with particular attention to semiconductors at and out of equilibrium
Capability to apply the relevant simplifications and approximations to the semiconductoir equations in the practically most important cases.  Capability to draw the band diagram of a semiconductor structure and to derive from it the qualitative electrical behaviour, both at equilibrium and out of equilibrium Knowledge of the properties of a semiconductor in equilibrium Knowledge of the main transport parameters of electron and holes in a semiconductor Detailed knowledge of the main equations used to describe the behaviour of semiconductors in equilibrium and out of equilibrium Capability to apply the required simplifications and approximations to the semiconductor equations in the practically more important cases Capability to define the band diagram in a semiconductor structure and to derive qualitatively its electrical behaviour, both in equilibrium and out of equilibrium Capability to foresee the charge distrinution in a pn junction for uniform and nonuniform doping profiles. Capability to relate the offequilibrium behaviour of a junction diode to the main charge transport phenomena: forward and reverse bias, breakdown Capability to derive the large and smallsignal models of a junction diode, and to relate them to the experimental behaviour Knowldege of the basic principles of photovoltaic conversion by means of semiconductor structures Knowledge of the operating principle of bipolar junction transistors (BJTs) and of the equations defining their static behaviour, and capability to relate them to the static characteristics Capability to derive the large and smallsignal models of a BJT, and to relate them to the experimental behaviour Knowledge of the operating principle of field effect transistors (FETs) Detailed knowledge of MOS systems in terms of charge distribution in the various operating regions: depletion, weak and strong inversion, accumulation Knowledge of the long channel MOSFET static behaviour, and of the main effects taking place for short channel lengths Capability to derive the large and smallsignal models of a MOSFET, and to relate them to the experimental behaviour Knowledge of the floating gate devices used in nonvolatile memories 
Prerequisites / Assumed knowledge
The course assumes a good knowledge of solid state physics basics, in particular energy bands and charged carrier distributions in a crystalline material. Furthermore, a detailed knowledge is assumed for the main quantities describing materials of interest in electronics, such as electrical conductivity, dielectric constant and their dependence on operating conditions: temperature and frequency. Finally, the course requires the knowledge of circuit theory basics for the understanding of the equivalent electrical models used for the description of semiconductor devices.

Contents
The topics discussed during the course are:
Doped semiconductor band diagrams and evaluation of carrier concentrations Shockley equations Electrical conduction in sewmiconductors: drift and diffusion Mathematical model of semiconductors Applications of the mathematical model to some significant examples of off equilibrium semiconductors Equilibrium pn junction: band diagram and electrostatics Effect of an applied bias to a pn junction: depletion charge variation and depletion capacitance Measurement of the junction built in voltage based on the voltage/capacitance characterization Quasi Fermi levels and junction law Junction currents and static model evaluation Current distribution in forward and reverse bias Impact of the series resistance on the static characteristics Diode turn on voltage concept Junction breakdown effects Use of the pn junction for photovoltaic conversion Operating principle of the bipolar transistor BJT Currents and main parameters of the BJT in forward operation Carrier concentration calculation in the emitter, base and collector regions EbersMoll equations derivation and static model BJT in reverse operation, saturation and cutoff BJT static and smallsignal characteristics model MOS system: equilibrium band diagram and effects of the applied bias Population inversion Calculation of the semiconductor total charge as a function of bias Strong inversion MOS systems and threshold voltage calculation CMOS systems: n channel and p channel MOSFETs MOSFET gradual channel analysis Long channel static MOSFET model in the quadratic region and in saturation Substrate effect Large and smallsignal MOSFET model MOSFET short channel effects Floating gate devices and their applications in nonvolatile memories 
Delivery modes
Theoretical lectures and practice classes are used in the course.
Practice classes will allow the students to quantitatively apply the equations derived in class on semiconductor structures strictly related to realistic devices. The obtained results are compared to the characteristics of commercial devices. 
Texts, readings, handouts and other learning resources
The reference books, chosen among the following ones, will be introduced by the professor responsible for the course.
Lectures and practice classes will exploit the projection system so that all the produced material will be made available on the course website as pdf files. Suggested reference books are: S. M. Sze, Dispositivi a semiconduttore, Hoepli, 1991 G.Masera, C.Naldi, G.Piccinini, Introduzione all'analisi dei dispositivi a semiconduttore, Ed. Hoepli, 1995. F. Bonani, G.Masera, S. Donati Guerrieri e G. Piccinini Dispositivi e Tecnologie elettroniche CLUT 2007. G.Ghione Dispositivi per la Microelettronica McGrawHill 1998 
Assessment and grading criteria
The goal of the examination is to verify the knowledge of the topics listed in the Contents section and the capability to apply them to exercise solution. The exam is made of a written test and of a compulsory oral examination. Access to the oral examination requires a grade for the written examination at least equal to 18/30. The final grade is obtained combining both the written and oral part partial.
Written test (weight 0.5): consists of two exercises, one mainly oriented to the quantitative application of the equations introduced during the lectures and made available to the student through a "list of formulae", the second exercise is mainly devoted to assess the analysis capabilities acquired by the student; Oral test (weight 0.5): to gain access to the oral test the students must have gained an evaluation of the written test at least equal to 18/30. The oral examination is devoted to the assessment of a proper knowledge of the theory discussed during the lectures and will possibly include the discussion of the written test. The theoretical topics that may be discussed during the oral test are listed in the Contents section. Normally the oral test has to be taken right after the results of the written test are provided. 
