The invention discloses a GaN-based
laser diode epitaxial structure and a preparation method thereof. The GaN-based
laser diode epitaxial structure is sequentially provided with a GaN
single crystal substrate, an n-type GaN layer, an n-type limiting layer, a lower
waveguide layer, an active region, an upper
waveguide layer, a p-type limiting layer and a p-type GaN layer from bottom to top in a stacked mode, wherein the lower
waveguide layer is an n<->-Aly2Ga<1-y2>N+n<->-GaN+n<->Inx1Ga<1-x1>N / GaN
superlattice composite waveguide layer; the active region is of an asymmetrically doped InGaN / GaN
double quantum well structure, and the upper waveguide layer is of a u<->Inx4Ga<1-x4>N / GaN
superlattice and u<->GaN+p<->Aly4Ga<1-y4>N
composite structure. The brand-new GaN-based
laser diode epitaxialstructure is obtained by optimally designing a GaN-based laser high-
quantum-efficiency gradient In component trapezoidal active region structure and further designing a novel optical waveguide layer structure. The GaN-based
laser diode epitaxial structure is used as a laser, and when optical pump lasing is carried out, the half-peak width is narrow, and the
light beam quality is high.