Namely, the band gap and n type doping of {HEAD ~ the wide band gap layer} are adjusted to suppress {TAIL ~ diffusion} of the thermally excited carriers 
Namely , the band gap and n type doping of { HEAD ~ the wide band gap layer } are adjusted to suppress { TAIL ~ diffusion } of the thermally excited carriers
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH