Electronic states due to point defects

Any point defect modifies the crystal potential of the structure [i.e. U(r) in the Schrodinger Equation] locally and therefore perturbs the bands near it. For defects with atomic orbitals very similar to those of the matrix atoms this generally leads to a 

Deep levels are states derived from the point defect atomic orbitals, regardless of the energy difference between the state and the appropriate band edge. An 

Charge state before eapture of a minority earrier Doubly charged, opposite to minority carriers Singly charged, opposite to minority carriers 

Cross seetion for minority carriers before eapture 10 to 10 cm (strongly attractive) 10 to 10 cm (moderately attractive) 

Cross seetion for majority carriers after eapture 10-18-10-20 2 (moderately repulsive) 10 to 10 cm (neutral) 

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