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

146

• 7. Semiconductor
• 7. Semiconductor

7.1. Bandstructure

direct gap indirect gap

147

7.2. Semiconductor bandstructure

• 7. Semiconductor

148

7.2. Intrinsic semiconductor

• 7. Semiconductor

149

7.3. Doping of semiconductors

• 7. Semiconductor

Donor Acceptor

150

7.3. Carrier density

• 7. Semiconductor

151

7.4. pn-junction

• 7. Semiconductor

diffusion (recombination) current: e in n p, h in p n in equilibrium: Igen = Irec , 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: field (generation) current: e generated in p n h generated in n p +++

• 152

7.4. pn-junction

• 7. Semiconductor

Schottky´s approximation (square charge distributions) Space charge region

153

7.4. pn-junction

• 7. Semiconductor

154

7.4. pn-junction

• 7. Semiconductor
• pen circuit

forward bias reversed bias

155

7.4. pn-junction

• 7. Semiconductor

156

7.5. Bipolar transitor

• 7. Semiconductor

First transistor - Bell labs 1947 p-n-p transistor – planar technology

157

7.5. Transitors

• 7. Semiconductor

158

7.5. Transitors

• 7. Semiconductor

159

7.5. Transitors

• 7. Semiconductor

Basis-Kollektor in Sperrrichtung Basis-Kollektor in Durchlassrichtung

Kollektorstrom ~ Emitterstrom hohe Stromverstärkung ß IC = ß . IB

160

7.5. MOS diode

• 7. Semiconductor

161

7.5. MOS diode

• 7. Semiconductor

a) Accumulation b) Depletion c) Inversion

162

7.5. MOS diode

• 7. Semiconductor

a) Accumulation b) Depletion c) Inversion

163

7.5. MOSFET

• 7. Semiconductor

VT: Spannung für die Inversionskanal (n) existiert VG: gate Spannung VD: drain Spannung VD > 0 bedeutet ndrain-p Übergang in Sperrrichtung VD = VDsat >> 0 ndrain-p Verarmungszone ausgedehnt, leitender Kanal wird eingeschnürt (= pinch-off point) VD > VDsat ndrain-p Verarmungszone weiter ausgedehnt, leitender Kanal wird zurückgedrängt, Injektion von Elektronen aus Kanal in p-Schicht und Absaugen in ndrain analog zu Bipolartransitor, Drainstrom ID in Sättigung

164

7.5. MOSFET

• 7. Semiconductor

165

7.6. Hall Effect E ⊥ B

• 7. Semiconductor

Non-closed orbits or carriers with different mobility or concentration ⇒ RH depends on magnetic field B

166

7.6. Hall Effect E ⊥ B

• 7. Semiconductor

MOSFET Inversion layer

Leads to quantization into levels En 2d - electron gas

167

7.6. Quantum Hall Effect

• 7. Semiconductor

Quantum Hall Effekt

NP 1985, Klaus v. Klitzing

Shubnikov - de Haas

Oszillationen des Magentowiderstands

168

7.6. Quantum Hall Effect

• 7. Semiconductor

Transport via 1d edge channels