What is typical values of impurity concebtration to change band stucture?

Question

Hello,

I am interesting in researching of impurities affect on dos

and band structure. Maybe someone can help me with a start point, and answer on my questions:

1. What is the minimum concentration of impurities (for scintillators) shous be, to affect dos and band structure?

2. What is the maximum number of impurities, when people stop to consider they as inpurities, but as the complete structure?

Thanks

Comments

the second question is amazing. You can also see the impurities locations as the total structure and the crystal as a kind of vacuum. It works also if you consider rather the defects resulting from impurities at large. One works always with materials having a given homogeneity such he can derive appropriate scale symmetries and invariants. Impurities might be very rare while their effects are noticiable. Some talk of impurities until a few percents because the general approaches remain more or less effective to interpret large scale properties.