A light-emitting device includes a substrate having a top surface, wherein the top surface includes a first portion and a second portion; a first semiconductor stack including a first upper surface and a first side wall, wherein the first semiconductor stack is on the first portion; a second semiconductor stack including a second upper surface and a second side wall, wherein the second semiconductor stack is on the first upper surface, and wherein the second side wall is devoid of connecting the first side wall; a plurality of first concavo-convex structures on the first portion; and a plurality of second concavo-convex structures on the second portion; wherein the first side wall and the second portion of the top surface form an acute angle α between thereof; and wherein the second concavo-convex structures have smaller size than that of the first concavo-convex structures.