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Mechdude

- 117

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## Homework Statement

A sample of silicon is purified until it contains only [itex] 10^22 [/itex] donors per [itex] cm^3[/itex] . Below what temparature will it cease to show intrinsic behaviour? ( take [itex] E_g = 1eV [/itex] ; [itex] E_d = 0.05eV [/itex] ; [itex] m_e =m_h = 0.2 [/itex]

## Homework Equations

for intrinsic semiconductors:

[tex] n_{i}^{2} = 4 \left[ \frac{k_B T} {2 \pi \hbar^2 } \right]^{3/2} (m_e m_h)^{3/4} e^{ \beta E_g /2} [/tex]

this is from his notes.

## The Attempt at a Solution

im i looking for the point at which [itex] n_i [/itex] is zero? or something else? and where does the [itex] E_d [/itex]which is [itex] =[/itex] donor ionization, fit in the equation?

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