Semiconductor structures including one, or more, III-nitride material regions (e.g., gallium nitride material region) and methods associated with such structures are provided. The III-nitride material region(s) advantageously have a low dislocation density and, in particular, a low screw dislocation density. In some embodiments, the presence of screw dislocations in the III-nitride material region(s) may be essentially eliminated. The presence of a strain-absorbing layer underlying the III-nitride material region(s) and/or processing conditions can contribute to achieving the low screw dislocation densities. In some embodiments, the III-nitride material region(s) having low dislocation densities include a gallium nitride material region which functions as the active region of the device. The low screw dislocation densities of the active device region (e.g., gallium nitride material region) can lead to improved properties (e.g., electrical and optical) by increasing electron transport, limiting non-radiative recombination, and increasing compositional/growth uniformity, amongst other effects.