In this case, the first, second and third semiconductor layers are formed of {HEAD ~ a non single crystal semiconductor} doped with {TAIL ~ a dangling bond neutralizer} 
In this case , the first , second and third semiconductor layers are formed of { HEAD ~ a non single crystal semiconductor } doped with { TAIL ~ a dangling bond neutralizer }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL