Chapter27_Carrier-Generation

Chapter27_Carrier-Generation - 2.7 Carrier Generation &...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
2.7 Carrier Generation & Recombination Perturbation of semiconductor, i.e. an excess or deficit in carrier concentration with respect to the equilibrium values is created, resulting in non-equilibrium conditions If the perturbation is removed, recombination/generation (R-G) processes will restore equilibrium conditions; if perturbation is maintained, R-G processes will stabilize the (non-equilibrium) carrier concentrations 2.7.1 Generation and Recombination Processes 2.7.2 R-G Statistics 2.7.3 Continuity Equations Literature: Pierret, Chapter 3.3-3.5.1, page 105-132 Slides courtesy of Prof. Oliver Brand
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 2.7.1 Generation/Recombination Processes Band-to-band R-G processes “only” involve electron in conduction band and hole in valence band R-G center generation/ recombination requires R-G center (lattice defect or impurity which generates states in the bandgap) Auger recombination requires 3 carriers (either 2 holes and 1 electron or 2 electrons and 1 hole) All processes occur at all times (even in equilibrium), with the process having the highest rate dominating Recombination Generation Pierret, Fig. 3.15
Background image of page 2
3 Momentum Considerations Band-to-Band vs. R-G Center R-G Processes What is the dominant R-G process, i.e. the process proceeding at the fastest rate, in a particular system? When do band-to-band R-G processes dominate over R-G center R-G processes and vice versa? Photons carry energy but very little momentum Phonons carry momentum but very little energy In indirect semiconductors , band-to-band recombination requires the emission/ absorption of a phonon (for momentum conservation) in addition to photon emission, making this process negligible compared to R-G center recombination In direct semiconductors , band-to-band recombination proceeds at a much faster rate, making these materials suitable for light emitting devices, e.g. LEDs and lasers Pierret, Fig. 3.18 Direct Semiconductor (e.g. GaAs) Indirect Semiconductor (e.g. Si or Ge)
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 Perturbation: Carrier Injection/Generation Processes: Photogeneration Operation of diode in forward direction Impact ionization p n > n i 2
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 19

Chapter27_Carrier-Generation - 2.7 Carrier Generation &...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online