
#1
Mar2813, 01:26 PM

P: 374

Dear forum,
in a diode semiconductor, the N region is rich in electrons. The P region is rich in holes. Is the number of extra electrons in the N region equal, larger or smaller than the number of holes in the P region? If so, why? Also, in the N region, it is said that the majority carriers are the electrons. I get that. The minority carriers are the holes....but there are no holes in the N region so how can there be any minority carriers at all? Thanks, fisico30 



#2
Mar2813, 01:42 PM

Sci Advisor
PF Gold
P: 2,020

The number of electrons/holes is a function of doping and can be controlled by the device designer. The doping saturates at around 10^19 cc1, which is called "extrinsic" doping. It gives the highest conductivity possible which is useful near the electrode connections.
You can inject holes into the n region, where they live for a time (the mean recombination time) before meeting electrons and annihilating. Transistor action is caused by minority carriers injected across the base region into the collector. 



#3
Mar2813, 01:42 PM

Sci Advisor
P: 3,380

No, at nonzero temperature, even in equilibrium there are both electrons and holes present in both the n and p region. They fulfill a equilibrium constant equation ##n_en_h=K(T)##. On the n side ##n_e=n_{0e}n_h\approx n_{0e}## and thus ##n_h\approx K/n_{0e}## where ##n_e## is the number density of electrons ##n_h## the number density of holes and ##n_{0e}## the number density of donor atoms.
A similar equation holds for the p side. 


Register to reply 
Related Discussions  
Finding the combined centroid of two regions given the centroids of both regions  Calculus & Beyond Homework  3  
Radiation Diode Detector Doping question.  Atomic, Solid State, Comp. Physics  5  
Simple Diode Analysis Problem  Calculating Current/Voltage in a diode:  Engineering, Comp Sci, & Technology Homework  1  
Inductor, switch, snubber diode(flyback diode)  Electrical Engineering  2  
Can any one explain about electron doping and Hole doping  Atomic, Solid State, Comp. Physics  1 