According to an embodiment of a method of fabricating III-Nitride semiconductor dies, the method includes: growing a III-Nitride body over a group IV substrate in a semiconductor wafer; forming at least one device layer over the III-Nitride body; etching grid array trenches in the III-Nitride body and in the group IV substrate; forming an edge trench around a perimeter of the semiconductor wafer, the grid array trenches terminating inside the group IV substrate; and forming separate dies by cutting the semiconductor wafer approximately along the grid array trenches.