Theoretically speaking the quantum well may be in the shape of a rectangular well

sandwiched between an n-type electron emitter with the conduction band edge lying above that of the well with sufficient energy to prevent the back injection of the electrons and p-type material with valence band edge lower than that of the well such that the holes will be injected easily in the well from the p-type emitter.

Also the difference in the valence band edges must be high enough to reduce back injection. The LED is constructed by double injection structure into a middle well. It is so that when the electrons and holes are injected in the well they will be trapped there and confined into well.

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