Point defect implementation

Point defects can be:

• Native defects, such as interstitials, vacancies, neutral (I, V) or charged (IP, IM, VM, VMM, VP, VPP).
• Substitutional dopants pairs, such as Bi (boron + interstitial), AsV (arsenic + vacancy), etc.

Break-up

Break-up is a mechanism for splitting a point defect: Ai -> A + I or AV -> A + V.

The break-up frequency is calculated by DADOS with an Arrhenius plot:

 Where:

• D_o,bk is the prefactor of break-up in diffusivity units for point defect Ai.
• λ is the jump distance.
• Eb_? is the binding energy for for point defect Ai.
• Em_? is the migration energy for I or V.
• See symbol list.

Captures

A capture can occur when a particle or defect is sufficiently near to another particle or defect and the capture is allowed. DADOS uses a capture distance called λ.

If the particle arrives in a very populated area, where more than one interaction is possible, DADOS randomly selects one.

A capture is always associated to an interaction.

For extended defects, such as amorphous pockets, I311, dislocation loops or voids, the captures depend on the surface, because it is there where the interaction occurs. Therefore, the larger the surface is, the capture will happen more frequently.

Jumps

Mobile particles in DADOS jump at a rate that is determined by both energy and temperature.

The implemented jumping directions are six: +x, -x, +y, -y, +z, -z.

Jump distance

Jump distance is called λ. We take it also to be equal to the capture distance.

• Its value is 0.384 nm, corresponding to the second neighbors distance in the silicon lattice.

• It is involved into the relation between the migration rate and the diffusivity:

 Jump frequency

Jump frequency is calculated by using Em_? and Dm_?:

     Where:

• D_m? is the prefactor of diffusivity for particle "?", Dm_?.
• λ is the jump distance.
• E_m? is the migration energy for particle "?", Em_?.
• See symbol list.

Pile-up

When a mobile dopant meets an amorphous pocket or an extended defect (I311 or void), the interstitial or vacancy is included into the extended defect whereas the dopant keeps very near to the defect but not included in it. It is, then, simulated as a point defect.