wherein the first, second and third semiconductor layers are formed of a non single crystal semiconductor doped with {HEAD ~ a dangling bond neutralizer}; the first and third semiconductor layers have {TAIL ~ the same conductivity type}; and the second semiconductor layer has a higher resistivity than the first and third semiconductor layers; and 
wherein the first , second and third semiconductor layers are formed of a non single crystal semiconductor doped with { HEAD ~ a dangling bond neutralizer } ; the first and third semiconductor layers have { TAIL ~ the same conductivity type } ; and the second semiconductor layer has a higher resistivity than the first and third semiconductor layers ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH