What is type 1 and type 2 semiconductors?

Type 1 Semiconductors: The bandgap of one semiconductor is completely contained in the bandgap of the other one. In double heterostructure design carriers will be confined in the smaller bandgap material. this structure is used to form barrier/quantum well in Multi quantum well lasers and LEds

Type II: like Type I The bandgap of the two materials overlap but the changes in the conduction and valence bands change sign. this type of materials do not use for light emiiting application as carriers can not be confined.