On the substrate, a first type conductivity layer, {HEAD ~ a first main layer} such as {TAIL ~ an active layer}, which has any one of an undoped type, a first type conductivity and a second type conductivity, and a second type conductivity layer are formed in this order 
such as
On the substrate , a first type conductivity layer , { HEAD ~ a first main layer } such as { TAIL ~ an active layer } , which has any one of an undoped type , a first type conductivity and a second type conductivity , and a second type conductivity layer are formed in this order
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH