EE5164 Semiconductor Properties and Devices II
Spring 2000
Prof. Richard A. Kiehl
Tuesday & Thursday, 11:00 a.m. - 12:15 pm, EE/CSci Rm 3125
Office Hours: Tues. 3:00-4:00 pm. Weds. 11:00 am — 12:00 pm
1 Overview
2 Intervalley transfer and carrier avalanche
Multivalley bandstructure, intervalley transfer, v-E characteristics.
Space-charge wave instabilities. Transferred electron effect and devices.
Impact ionization. Role of energy and momentum conservation.
Phase delays due to avalanche and drift. Avalanche microwave devices.
Influence of microwave circuits on internal carrier dynamics.
3 Real space transfer & electron tunneling
Lateral transport in heterostructures.
Real space transfer of carriers.
Monte Carlo simulations.
Real space transfer devices.
Tunneling barriers: heterostructures, metal-oxide-metal, quantum size effects.
Influence of density of states on tunneling.
Tunneling in PN junctions.
Tunneling devices.
4 Basic transistor concepts
Basic transistor concepts:
FET (electrons controlled spacially separated electrons)
Bipolar (holes control electrons),
Hot electron transistor (cold electrons control hot electrons),
5 Metal Insulator Field Effect Transistor (MESFET) - 1
Gradual channel approximation.
Shockley model.
Two- piece velocity-field model
6 MESFET 2
Threshold voltage.
Simple capacitor picture.
Gm/C.
Operation modes: depletion, enhancement, amplification
Non-ideal effects, domains, actual velocities, gate recess, gate current, gate resistance.
7 Heterostructure field Effect Transistor (HFET) - 1
Optimiation for lateral transport and low voltage operation.
Bandgap vs lattice constant for various materials.
Basic modulation doped (MODFET) structure and advantages.
Parallel conduction in MODFET’s.
Threshold voltage.
2DEG physics.
8 HFET - 2
Density of states in triangular well.
Screening issues for parallel channels.
Comparison of gate current MESFET vs MODFET.
Delta doping charge distributions.
Lateral bandstructure (source-to-drain) picture.
Hot-electron gate current.
9 HFET - 3
Effective masses for Si/SiGe and III-IV compound material systems.
Alternate HFET structures: MODFET, MISFET, SISFET.
Doping, DX center, and gate leakage issues.
Effect of gate leakage current on transconductance.
Quantum well channels
Valence band E-k diagram.
10 HFET 4
p-type MODFET.
Strained layer FET channels.
Effects of band nonparabolicity.
Quantum confinement effects.
Surface roughness scattering.
Complementary n- and p-HFET’s.
11 Metal Oxide Semiconductor (MOS) basics - 1
Basic structure.
Role of gate material and substrate doping and characteristics.
Band diagram in flat band and operational bias conditions.
Charge distributions.
Importance of S-D doping versus channel doping.
Threshold voltage issues for MOSFET IC’s.
The CMOS inverter.
12 MOS basics — 2
Accumulation, depletion, and inversion regimes.
Carrier distributions near oxide/Si interface for various regimes.
Frequency response and dynamics of carriers.
Influence of thermal tail of carrier distributions, generation-recombination, ohmic contact to carriers.
13 Review for midterm
14 MOS capacitor 1
Surface charge vs surface potential plot.
Inversion and depletion charge.
Ideal capacitance voltage curve
Effect of non ideal charges on capacitance-voltage (CV) characteristics.
Interface states.
Threshold voltage calculation.
15 MOS capacitor 2
Frequency response of CV.
Sources of oxide charge.
Extraction of parameters from CV characteristics.
16 MOS Field Effect Transistor (MOSFET) - 1
Current-voltage characteristics.
Gradual channel and Shockley model.
Charge control two-piece velocity-field characteristic.
17 MOSFET - 2
Short channel effects.
Output conductance.
Subthreshold current.
Drain induced barrier lowering.
Punch through.
Avalanche breakdown.
Hot electron injection.
18 MOSFET - 3
Integration of p and n MOSFET’s.
Silicon on insulator.
19 MOSFET - 4
Semiconductor Industry Association projections for the future CMOS.
Scaling laws.
State-of-art structures, low-K dielectric, high-K gate dielectric, body doping.
Threshold voltage issues.
20 MOSFET - 5
Alternative geometries: dual gate variations, vertical structures.
Fabrication of alternate structures.
Advanced floating gate memory structures.
21 Bipolar Transistors - 1
Basic band diagram.
Strength and weaknesses.
Minority carrier diffusion.
Current components in different modes.
22 Bipolar Transistors - 2
Details of minority carrier distributions.
Doping gradient.
Gummel number.
23 Bipolar Transistors - 3
Early effect (base modulation).
Kirk effect (base push out).
Contributions to base current.
24 Bipolar Transistors - 4
Current gain for moderate Vbe
Resulting design optimization for homojunction bipolars.
Current gain over wide Vbe range.
25 Bipolar Transistors - 5
Basic Ebers-Moll model.
Extension to include parasetics
Limits of Ebers-Moll model.
Comments on Gummel Poon model.
26 Heterostructure Bipolar (HBT) - 1
Delays.
Generalization of heterojunction bipolar (HBT)
Levels of analysis: diffusion, diffusion+drift, generalization for HBT.
Charge storage approach to delay calculation.
27 Heterostructure Bipolar 2
Total delay.
Basic ac response from delay analysis.
HBT advantages and problems.
28 Nanoscale and novel devices
Novel devices based on new physical mechanisms.
Low dimensional structures.
Quantum interference.
Single-electron tunneling devices
Nanoscale fabrication, nanoassembly.
29 Review for Final