Surface p+ doping to supress surface state generation

[leohart]

p+ doping

We know that surface states at the si-sio2 interface will act as generation/recombination centers.this is abosulutely not wanted for photodiode applications,because this gives large dark current.
A pinned photodiode uses a surface p+ implant to reduces the collection of this dark current by surface states.But how what's the mechnism behind this doping?

 

[A.Anand Srinivasan]

the action of the p+ regions is to restore the potential wells so that there no absorption of charge due to the irregularity in the potential well and hence leading to reduction in dark current....

 

[leohart]

Do you mean there is no depeletion area in p+ area(they are at the p+ and nwell interface and most in lower doped nwell),so no generated e/h pair in p+(also is si/sio2 surface with lots defects)will seperated by the electric field and gathered as dark current??

But I remebered that was all about fermi level and g/r center(trap) filling and depeletion thing...

 

[A.Anand Srinivasan]

by saying the filling of the potential well i meant the adjustment in the energy(fermi) level such that the absorption of e emitted due to the radiation is reduced.....

 

[leohart]

by saying the filling of the potential well i meant the adjustment in the energy(fermi) level such that the absorption of e emitted due to the radiation is reduced.....

Yeah,that is what I want to know!
Can you recommend any books or papers on this?Few textbooks talk this carrier trap(G/R center) stuff in detail...

Added after 2 minutes:

the action of the p+ regions is to restore the potential wells so that there no absorption of charge due to the irregularity in the potential well and hence leading to reduction in dark current....

How comes the irregularity in the potential well?I think at the sio2/si surface,it is n doped so the fermi level is above intrinsic level,right?

 

[A.Anand Srinivasan]

the surface interaction between SiO2 and Si would be irregular at the interface and this leads to the surface state generation..... I'm not sure of books and references for this topic....