1. FROM DOPED SEMICONDUCTORS TO SEMICONDUCTOR DEVICES
Materials
Doping
Electronic bands
Junctions
Architectures
Electronic and optical devices

3. Isomorphous substitution Isomorphous substitution

4. HYDROGENIC MODEL FOR DOPANT IONIZATION LEVELS IN EXTRINSIC SEMICONDUCTORS
Hydrogenic doping model of n-donors and p-acceptors
Insert a neutral P in place of a neutral Si in substitutional site of the diamond lattice
Extra electron, which cannot be placed in VB, is loosely associated with this center
Much the same way electron in Bohr H electron is attached to the central proton

5. HYDROGENIC MODEL FOR DOPANT IONIZATION LEVELS IN EXTRINSIC SEMICONDUCTORS
Interaction energy is decreased by the effective dielectric constant of Si ( = 12) compared to vacuum ( = 1)
Also the effective mass m* of e in Si is about 0.2me
Bohr energies and radii thus need to be modified for n-doped Si to take these accounts into effect

6. EH = -e4m*/8o22h2n2 rH = n2h2o/e2m*
HYDROGENIC MODEL FOR DOPANT IONIZATION LEVELS IN EXTRINSIC SEMICONDUCTORS
EH = -e4m*/8o22h2n2
rH = n2h2o/e2m*
Combined effect of higher  and lower m* for Si
1st IP of P donor being about 200 x less than H (0.044eV)
0.53 Å Bohr radius expands to ~ 12.5 Å spanning many Si atoms

9. Continuous Tuning of the Fermi Energy of a Semiconductor by Varying the Dopant Concentration

15. SILICON SOLAR CELL
p-dope with extra B holes
n-dope with extra P electrons

16. GaAs LED
p-dope with extra Ga holes
N-dope with extra As electrons

18. SCHOTTKY BARRIERS, SEMICONDUCTOR-METAL JUNCTIONS
Electron energy level diagrams showing the formation of a Schottky barrier between a metal and an n-type semiconductor
At equilibrium (open circuit), VS is the potential drop across the space charge region

19. SCHOTTKY BARRIERS, SEMICONDUCTOR-METAL JUNCTIONS
VS = EF(M) -EF(SC)
Schottky diode behavior under forward and reverse bias  

20. V Schottky Barrier SC-Au Junction Solar Cell
Photovoltaic effect in n-Si/Au V CB VB Ef n Au
n-Si
Voc e hv h Au
interface
n-Si
Voc determined by E(F)Si - E(F)Au and photon to electron conversion efficiency  depends on efficiency of e-h separation (current generation) versus h - e recombination

21. INCREASING THE NUMBER OF JUNCTIONS, THE n-p-n JUNCTION TRANSISTOR
By extending the concept of the single p-n junction diode we can move to the double junction n-p-n junction transistor, and see how amplification and switching action naturally emerges.
Basis of the monumental discovery by Brattain, Schockly and Bardeen at Bell Laboratories in 1948, followed shortly after by the integrated circuit of Groves, also at Bell
Beginning of the global information revolution

22. INCREASING THE NUMBER OF JUNCTIONS, THE n-p-n JUNCTION BIPOLAR TRANSISTOR
Electrons are effectively pumped from the left n-region under forward bias through the p-region to the right n-region under reverse bias
The same number of electrons are involved but their energy has been amplified from IV1 to IV2 that drives them round the circuit

23. INCREASING THE NUMBER OF JUNCTIONS, THE n-p-n JUNCTION BIPOLAR TRANSISTOR
Voltage amplification
V2/I = R2
V1/I = R1
V2/V1 = R2/R1  
Can also function as a current amplifier and an electrical switch (bias voltage on base)

24. BAND DIAGRAM FOR n-p-n JUNCTION BIPOLAR TRANSISTOR
Tuning the bending of the CBs and VBs in a two junction SC device by voltage biasing to create an electron pump!!!
Forward and reverse voltage biasing causes the electrons to be pumped from the left n-type emitter to right n-type collector passing through the p-type base

25. METAL OXIDE SEMICONDUCTOR FIELD EFFECT TRANSISTOR MOS-FET
MOS-FETs are basic electronic switches found in silicon chips
Each MOS-FET can be switched current on or current off, representing a "1" or "0", known as binary code
All computation is done using different combinations of these two outputs to do calculations
Modern chips contain millions of transistors allowing them to execute millions of calculations per second
p-Si
n-Si
oxide

26. METAL OXIDE SEMICONDUCTOR FIELD EFFECT TRANSISTOR MOS-FET
The tiny MOS-FET devices consist of a conducting source, drain and gate with a metal oxide insulator between the gate and semiconductor
p-channel MOS-FET - a threshold positive voltage applied to the gate repels holes from p-channel and allows electrons to flow between source and drain electrodes and thereby turns the device on at a critical gate voltage
Removing gate voltage switches it off
p-Si
n-Si
oxide

27. Need long excited state lifetime for inversion
e-h radiative recombination
100% reflecting
<100% reflecting

28. Narrow Eg(GaAs) sandwiched by wide Eg(n,p-AlxGa1-xAs) – Eg composition tuning
QSE tuning of Eg