Semiconductors — Class 11 Maharashtra HSC Physics revision notes
A 6-page visual revision sheet for Semiconductors, written for Class 11 Maharashtra HSC Physics. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.
Page 1 as PDF
Semiconductors in one look
band theory, intrinsic and extrinsic silicon, and the p-n junction diode
Conductors, insulators, semiconductors
- conductivity σ = nqμ
- n is carrier density, q the carrier's charge, μ its mobility
- conductors (metals): about 10^28 free electrons per m^3
- conductivity falls as temperature rises
- insulators: only about 10^7 free electrons per m^3, effectively none
- semiconductors: conductivity between the two, tailorable
- unlike a metal, conductivity rises with temperature
- silicon, germanium are elemental semiconductors, group 14, valence 4
- each atom covalently bonded to four neighbours in a tetrahedral lattice
Band theory, in brief
- an isolated atom's electrons occupy discrete energy levels
- in a solid, Pauli's exclusion principle splits each level into a huge number of sub-levels
- these sub-levels appear as a continuous energy band
- topmost occupied band: the valence band
- next higher band, where conducting electrons live: the conduction band
- the band gap: the empty range between them
- roughly 1.12 eV for silicon, 0.66 eV for germanium at 300 K
- about 5.47 eV for diamond
- metal: valence and conduction bands overlap, easy to conduct
- insulator: gap is wide (sim5 eV), hard to cross
- semiconductor: gap is small (about 1 eV), thermal energy alone crosses some electrons
Page 1 of 6. The full sheet, all 6 pages, opens free in the app.
What this Semiconductors sheet covers
- Conductors, insulators, semiconductors
- Band theory, in brief
- Conductivity and the band gap
- Metal, semiconductor, insulator
- Intrinsic semiconductors
- Heat makes pairs
- A field moves them
- Doping and extrinsic semiconductors
- n-type vs p-type
- n-type
- p-type
- The p-n junction
- Diffusion and the depletion region
- The potential barrier
- Forward vs reverse bias
- Forward bias
- Reverse bias
- The junction diode
- static (DC) resistance
- dynamic (AC) resistance
- The diode as a rectifier
- Rectifiers at work
- Other junction devices
- Symbols
- Traps that cost marks
- Tricks that save time
How CapCompass uses this sheet
These notes are not a standalone PDF. CapCompass plans Physics chapter by chapter against your real exam dates and free hours, and when the plan reaches Semiconductors the sheet opens inside the study block itself — at the page covering the sub-topic that block is on, with the timer still running. Revision arrives at the moment the plan says revise, instead of having to be gone looking for.