Semiconductor laser diode

A vertical-cavity surface-emitting laser (VCSEL), comprising:

• a GaAs substrate;
• and
• a multi-layer structure on the GaAs substrate, wherein the multi-layer structure comprises:
• a lower epitaxial region, located on the GaAs substrate;
• an active region, located on the lower epitaxial region, wherein the active region comprises a first active layer, an epitaxial region and a second active layer, the epitaxial region is disposed between the first active layer and the second active layer, the first active layer comprises one or more quantum well structures or one or more quantum dot structures, and the second active layer comprises one or more quantum well structures or one or more quantum dot structures;
• and
• an upper epitaxial region, located on the active region,
• wherein the epitaxial region further comprises a tunnel junction and a hole blocking layer, the hole blocking layer is disposed between the tunnel junction and the first active layer or between the tunnel junction and the second active layer for blocking the holes in the first active layer or the second active layer from reaching the tunnel junction, and the hole blocking layer comprises a material selected from the group consisting of InGaAsP, InGaAsPN, InGaAsPSb, InGaAsPBi, InGaP, InGaPN, InGaPSb, InGaPBi and InAlGaAsP.