Range of Holes Flow in pn junction diode
The distance that minority carriers can move across the other material is called the "diffusion distance". The time that it takes until the minority carrier disappears is called the "minority-carrier recombination lifetime". 

The distance / time that minority carriers have is dependent on the number of recombination sites in the base material. Recombination sites are crystal defects.

If your majority carrier has better mobility than your minority carrier, you want to create more recombination sites close to the junction, so that your injected minority carriers are quickly converted to majority carriers.

Since electron mobility is better than hole mobility, you probably want your 
"diffusion distance" and "carrier recombination lifetime" to be shorter for holes on the N side, and to be longer for electrons on the P side.