SEMICONDUCTORS & ELECTRONIC DEVICES
                                    │
        ┌───────────────────────────┼───────────────────────────┐
        │                           │                           │
   ENERGY BANDS              p-n JUNCTION               LOGIC GATES
        │                           │                           │
   ┌────┴────┐              ┌───────┴───────┐           ┌───────┴───────┐
 Conductor  Semiconductor   Formation    Biasing      Basic Gates  Universal
 E_g=0    Insulator E_g>3eV     │           │              │        Gates
           Si:1.1eV            ↓       ┌───┴───┐       ┌──┴──┐    NAND+NOR
           Ge:0.67eV    Depletion  Forward Reverse   OR AND NOT
                        Region   (narrow) (wide)         │
                        Barrier  Current   Tiny        Special
                        ~0.7V Si  flows    current    ┌──┴──┐
                        ~0.3V Ge          →Breakdown NAND  NOR
        │                                             Y=(AB)' Y=(A+B)'
   CARRIERS                      │
   ┌─────┴──────┐          SPECIAL DIODES          DE MORGAN
 n-type      p-type         ┌────┴────┐         ┌───────┴───────┐
Pentavalent  Trivalent  ┌───┤  ├───┐         (A+B)'=A'·B'  (A·B)'=A'+B'
P,As,Sb    B,Al,Ga    Zener Photo LED Solar
$e^{-}$ majority $h^{+}$ majority Rev   Rev  Fwd  None
Both NEUTRAL            Reg  Detect Emit Generate
Mass Action: n_e×n_h=n_$i^{2}$     V_Z   Current Light  EMF

Central concept: Everything in this chapter connects to energy band theory. Carrier types → doping → junction behavior → special diodes → optical effects. Logic gates are digital applications using the diode's switching behavior.