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