Light-emitting device

A light-emitting device, comprising:

• a substrate;
• a first semiconductor layer and a second semiconductor layer, disposed on the substrate;
• an active layer, disposed between the first semiconductor layer and the second semiconductor layer;
• a first aluminum-containing semiconductor layer, disposed between the substrate and the first semiconductor layer, wherein a first aluminum composition ratio of the first aluminum-containing semiconductor layer is greater than an aluminum composition ratio of the first semiconductor layer;
• a second aluminum-containing semiconductor layer, disposed between the first aluminum-containing semiconductor layer and the first semiconductor layer, wherein a second aluminum composition ratio of the second aluminum-containing semiconductor layer is greater than the aluminum composition ratio of the first semiconductor layer;
• and
• a stack structure, disposed between the first aluminum-containing semiconductor layer and the second aluminum-containing semiconductor layer, and the stack structure comprising:
• a first indium-containing semiconductor layer, comprising Ina1Alb1Ga1-a1-b1N (0<a1+b1<1);
• a second indium-containing semiconductor layer, disposed on the first indium-containing semiconductor layer and comprising Ina2Alb2Ga1-a2-b2N (0<a2+b2<1);
• and
• a third indium-containing semiconductor layer, disposed on the first indium-containing semiconductor layer and comprising Ina3Alb3Ga1-a3-b3N (0<a3+b3<1), and 0<a3≤a1<a2 or 0<a1≤a3<a2.