Graded Index Separate Confinement Heterostructure (GrInSCH)
Graded Index Separate Confinement Heterostructure are an improvement on the confinement structure for semiconductor lasers. Unlike conventional heterostructures, where the band energy changes abruptly at the active region, as the graded part of the name suggests, the cladding materials are progressively doped so that the band gap of the cladding is reduced to meet the band gap of the smaller band-gap material.
Band structure of a GrInSCH.
GRInSCH structures are produced by altering the alloy concentration concentration during the growth process of the cladding materials. MBE or MOCVD can be precisely controlled.
Their efficiency is much higher than even conventional heterojunction lasers because the band gap of the semiconductor barriers reduce gradually until they reach the band gap of the active region as shown in the diagram. Heterojunction lasers are more efficient than homojunction lasers since carriers are confined to a smaller area and give rises to a lower threshold current. GrInScH not only confines the carriers but also confines the light emission.
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