How to know the PN diode voltage?

[pinpinpin]

A.
For Si:
(a)Nd=10^20 (cm^-3) Na=10^19 (cm^-3)
(b)Nd=10^19 (cm^-3) Na=10^17 (cm^-3)
(c)Nd=10^18 (cm^-3) Na=10^15 (cm^-3)
Questions:
1. Which one has the Largest turn on voltage? why???
2. Which one has the Largest breakdown voltage? why???
3. Which one is tend to occur Zener breakdown? Which one is tend to occur Avalanche breakdown? why???
4. Which one has the Largest junction capacitance?

B.
There are two pn diodes (Nd=10^19 (cm^-3) Na=10^17 (cm^-3) ) at 300K
For Si (Eg=1.1eV ni=1.5*10^10 (cm^-3) )
For Ge(Eg=0.66eV ni=1.4*10^13 (cm^-3) )
Question
1. Which one has the Largest turn on voltage? why???
2. Which one has the Largest breakdown voltage? why???
3. Which one has the Largest reverse saturation leakage current? why???

Please tell me the reason or formula of each question thanks a lot!!!:smile:

 

[errakeshpillai]

Capacitance:-
The one with the highest doping will have a narrower Potential Barrier. So its width will be the least compared to the others.
So according to the formula C = (A/ d), where d is the width., we get the capacitance as the largest.
Ok.