This preview shows page 1. Sign up to view the full content.
Unformatted text preview: Ion The extra electron and the extra hole cancel out A LITTLE MATH
n= number of free electrons p=number of holes ni=number of electrons in intrinsic silicon=10¹º/cm³ pi-number of holes in intrinsic silicon= 10¹º/cm³ Mobile negative charge = -1.6* 10-19 Coulombs Mobile positive charge = 1.6* 10-19 Coulombs At thermal equilibrium (no applied voltage) n* p=(ni)2 (room temperature approximation) The substrate is called n-type when it has more than 10¹º free electrons (similar for p-type) P-N Junction P-N
s s s s Also known as a diode One of the basics of semiconductor technology Created by placing n-type and p-type material in close Created contact contact Diffusion - mobile charges (holes) in p-type combine with Diffusion mobile charges (electrons) in n-type mobile P-N Junction P-N
s Region of charges left behind (dopants fixed in crystal Region lattice) lattice)
– Group III in p-type (one less proton than Si- negative Group charge) charge) – Group IV in n-type (one more proton than Si - positive Group charge) charge) s Region is totally depleted of mobile charges - “depletion Region region” region”
– Electric field forms due to fixed charges in the depletion Electric region region – Depletion region has high resistance due to lack of mobile Depletion charges charges THE P-N JUNCTION THE The Junction The The “ potent...
View Full Document
- Winter '08