wherein said {TAIL ~ semiconductor layer} has {HEAD ~ a diamond} or zinc blende crystal structure, and 
wherein said { TAIL ~ semiconductor layer } has { HEAD ~ a diamond } or zinc blende crystal structure , and
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH