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