Abstract: A III nitride epitaxial substrate which makes it possible to obtain a deep ultraviolet light emitting device with improved light output power is provided. A III nitride epitaxial substrate 10 includes a substrate 12, an AlN buffer layer 14, a first superlattice laminate 16, a second superlattice laminate 18 and a III nitride laminate 20 in this order. The III nitride laminate 20 includes an active layer 24 including an Al?Ga1-?N (0.03??) layer. The first superlattice laminate 16 includes AlaGa1-aN layers 16A and AlbGa1-bN (0.9<b?1) layers 16B which are alternately stacked, where ?<a and a<b hold. The second superlattice laminate 18 includes repeated layer sets each having an AlxGa1-xN layer 18A, an AlyGa1-yN layer 18B, and an AlzGa1-zN (0.9<z?1) layer 18C, where ?<x and x<y<z hold.

Abstract: An object of the present invention is to provide a method for producing a Group III nitride semiconductor epitaxial substrate, a Group III nitride semiconductor element, and a Group III nitride semiconductor free-standing substrate, which have good crystallinity, with not only AlGaN, GaN, and GaInN the growth temperature of which is 1050° C. or less, but also with AlxGa1-xN having a high Al composition, the growth temperature of which is high; a Group III nitride semiconductor growth substrate used for producing these, and a method for efficiently producing those. The present invention provides a Group III nitride semiconductor growth substrate comprising a crystal growth substrate including a surface portion composed of a Group III nitride semiconductor which contains at least Al, and a scandium nitride film formed on the surface portion are provided.