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