7. Semiconductor 7. Semiconductor 7.2. Intrinsic semiconductor 7. - PowerPoint PPT Presentation

7. Semiconductor 7. Semiconductor 7.2. Intrinsic semiconductor 7. Semiconductor 146 148 7.1. Bandstructure indirect gap direct gap 7.2. Semiconductor bandstructure 7.3. Doping of semiconductors 7. Semiconductor 7. Semiconductor 147 149 Donor Acceptor

7.3. Carrier density 7. Semiconductor 7.4. pn-junction 7. Semiconductor 150 152 Schottky´s approximation (square charge distributions) Space charge region 7.4. pn-junction 7.4. pn-junction 7. Semiconductor 7. Semiconductor 151 153 diffusion (recombination) current: e in n � p, h in p � n field (generation) current: e generated in p � n h generated in n � p +++ - - in equilibrium: I gen = I rec , μ = const. - space charge layer: fixed positively charged donors (in n) and negatively charged acceptors (in p) Electric field and potential according to Poisson equation:

7.4. pn-junction 7. Semiconductor 7.5. Bipolar transitor 7. Semiconductor 154 156 open circuit forward bias First transistor - Bell labs 1947 reversed bias p-n-p transistor – planar technology 7.4. pn-junction 7.5. Transitors 7. Semiconductor 7. Semiconductor 155 157

7.5. Transitors 7. Semiconductor 7.5. MOS diode 7. Semiconductor 158 160 7.5. Transitors 7.5. MOS diode 7. Semiconductor 7. Semiconductor 159 161 Kollektorstrom ~ Emitterstrom a) Accumulation Basis-Kollektor in Basis-Kollektor in hohe Stromverstärkung ß Durchlassrichtung Sperrrichtung I C = ß . I B b) Depletion c) Inversion

7.5. MOS diode 7. Semiconductor 7.5. MOSFET 7. Semiconductor 162 164 a) Accumulation b) Depletion c) Inversion 7.6. Hall Effect E ⊥ B 7.5. MOSFET 7. Semiconductor 7. Semiconductor 163 165 V T : Spannung für die Inversionskanal (n) existiert V G : gate Spannung V D : drain Spannung V D > 0 bedeutet n drain -p Übergang in Sperrrichtung V D = V Dsat >> 0 n drain -p Verarmungszone ausgedehnt, leitender Kanal wird eingeschnürt (= pinch-off point) V D > V Dsat n drain -p Verarmungszone weiter ausgedehnt, leitender Kanal wird zurückgedrängt, Injektion von Elektronen aus Kanal in p-Schicht und Absaugen in n drain analog zu Bipolartransitor, Drainstrom I D in Sättigung Non-closed orbits or carriers with different mobility or concentration ⇒ R H depends on magnetic field B

7.6. Hall Effect E ⊥ B 7. Semiconductor 7.6. Quantum Hall Effect 7. Semiconductor 166 168 Transport via 1d edge channels MOSFET Inversion layer Leads to quantization into levels E n 2d - electron gas 7.6. Quantum Hall Effect 7. Semiconductor 167 Quantum Hall Effekt NP 1985, Klaus v. Klitzing Shubnikov - de Haas Oszillationen des Magentowiderstands