Chapter 3 Lecture - Part 5

Drift of carriers in b and e fields drift

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: mobility is affected by the lattice and the impurities. – It has a temperature dependence because scattering It process have a temperature dependence. Drift of Carriers in B and E Fields Drift Conductivity • All charge carriers are in motion – for electrons and holes at equilibrium (no external fields) for the motion is random and lots of scattering occurs. the – Result: no net flow of charge Result: • With an applied external field, charge does flow With (drift): (drift): – It can be shown that for electrons, the current density Jx is given by: given Jx = -qn<vx> = q2ntEx/mx* = σEx and σ = qnµx and where: µn is the electron mobility and mx* is the where: conductivity effective mass (not DOS EM!) conductivity Randomized Electron Motion Thermal motion of an electron in a solid. Drift of Carriers in B and E Fields Drift • A similar analysis can be performed for holes, similar and the holes also have a mobility µ arrising from a current Jx for holes from p • Total current is the sum of electron and hole Total current: current: J = q(nµ + pµ )Ex = σEx n p • Also, there is an inverse relationship between Also, effective mass and mobility --> less massive particles are more mobile than massive ones. particles Current Flow Conventions Drift of electrons and holes in a semiconductor bar. Drift of Carriers in B and E Fields Drift • Temperature Effects and Doping on Mobility – Recall that ther...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online