If the layer is too thick {HEAD ~ the advantage} of confinement is lost, and if the layer is too thin carrier spillover may occur, both of which contribute negatively to {TAIL ~ the efficacy} of a solid state lighting source 
If the layer is too thick { HEAD ~ the advantage } of confinement is lost , and if the layer is too thin carrier spillover may occur , both of which contribute negatively to { TAIL ~ the efficacy } of a solid state lighting source
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH