Lecture_12

Lecture_12 - 4 PN Junctions Summary Review of semiconductor...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Prof. J. S. Harris 1 EE243. Semiconductor Optoelectronic Devices (Winter 2010) Review of semiconductor transport theory Continuity equation Current density equations Mobilities Diffusion Recombination mechanisms Diffusion length Debye length Dielectric relaxation time p-n junction diodes Depletion approximation 4. PN Junctions Summary Prof. J. S. Harris 2 EE243. Semiconductor Optoelectronic Devices (Winter 2010) There are three main classes of conduction band to valence band recombination processes • Radiative recombination • Recombination through traps • Auger recombination. Recombination
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 Prof. J. S. Harris 3 EE243. Semiconductor Optoelectronic Devices (Winter 2010) Auger recombination Auger recombination is a 3 carrier process which is the “reciprocal” of Avalanche Multiplication in that there are 3 carriers in the initial state and only a single free carrier in the Fnal state. The initial state can be either two electrons and one hole, or two holes and one electron, leaving the last free carrier with ~ E g kinetic energy after the recombination. Prof. J. S. Harris 4 EE243. Semiconductor Optoelectronic Devices (Winter 2010) In an Auger recombination event, e.g., with two electrons and one hole, one electron recombines with the hole and the energy of recombination is transferred to the remaining electron rather than a photon as in radiative recombination. Recombination rates in Auger processes therefore have form (4.28) r Auger = C 2 h p 2 n + C 2 e pn 2 where C 2h and C 2e are coefFcients corresponding to the 2- holes--1-electron process and 2-electrons--1-hole process respectively. Auger recombination
Background image of page 2
Prof. J. S. Harris 5 EE243. Semiconductor Optoelectronic Devices (Winter 2010) Because Auger recombination depends upon the product of the square of the majority carrier density x the minority carrier density ( n 2 p or np 2 , but in most cases, n 3 or p 3 since the electron and hole densities are equal in undoped QW regions), it is not important at low carrier densities. It is, however, quite important at carrier densities required for the operation of semiconductor laser diodes. This is especially true for longer wavelength laser diodes used for long distance telecommunications (e.g., 1.3 μ m and 1.5 μ m) In some cases, the bandgap energy is comparable to separation between valence bands (SO band), leading to a resonance enhancement of the 2-hole--1-electron recombination process. Auger recombination (2) Prof. J. S. Harris 6 EE243. Semiconductor Optoelectronic Devices (Winter 2010) Laser Recombination Characterization ) ( 3 2 1 Cn Bn An eV I a + + = 2 Bn TSE Tot Aug Tot Rad Tot Mono I I I I I I TSE d I d Z 3 2 1 )) (ln( )) (ln( 2 / 1 + + = Z n I ~ EDGE Active region GaAs waveguide GaAs waveguide p-AlGaAs mesa n-AlGaAs GaAs substrate p-metal END VIEW WINDOW n-metal I An or A p Trap Recombination Spontaneous Radiative Recombination Auger Recombination I Bnp I Cn 2 p or
Background image of page 3

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

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/05/2010 for the course EE 243 taught by Professor Harris,j during the Winter '10 term at Stanford.

Page1 / 17

Lecture_12 - 4 PN Junctions Summary Review of semiconductor...

This preview shows document pages 1 - 4. Sign up to view the full document.

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