Question

The diffusion length for holes LP, is the 
1. Average distance which an injected hole travels before recombining with an electron
2. Maximum distance travelled by a hole before recombining with an electron
3. Length of the region in which diffusion takes place
4. Minimum distance travelled by a hole before recombines with an electron

Answer 1

Correct Answer - Option 1 : Average distance which an injected hole travels before recombining with an electron

Carrier Lifetime (τ):

1) It is the interval from generation to recombination i.e. from breaking of the covalent bond until its recombination.

2) It is also the average lifetime of charge carriers.

\(L = \sqrt {D\tau } \)  ----(1)

Where L is called the length of diffusion which depends on charge carriers, mobility of carriers, carrier lifetime, and also temperature.

Diffusion length is the average length a carrier moves between generation and recombination. 

SI unit of L is cm.