{HEAD ~ Thermally excited carriers} generated in {TAIL ~ a first n type compound semiconductor layer} tend to diffuse in the direction of a π layer  
generated in
{ HEAD ~ Thermally excited carriers } generated in { TAIL ~ a first n type compound semiconductor layer } tend to diffuse in the direction of a π layer
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH