By eliminating the influence of surface recombination, the reported consideration that on‐resistance of GaN p+n diodes fabricated on free‐standing substrates should be limited by nonradiative recombination around dislocation lines is validated. The validation is based on analyses of 1) bulk nonradiative recombination current densities (Jnr), determined from the y intercept of forward‐current density/inverse of anode radius plots, of diodes fabricated on two kinds of vapor‐phase epitaxially grown freestanding substrates (i.e., maskless 3D M‐3D, dislocation density Ndis ≤ 4 × 105 cm−2 and void‐assisted separation VAS, Ndis = 1–4 × 106 cm−2) and 2) distributions of two‐photon photoluminescence (2PPL) from an n‐GaN layer identifying dislocations as dark spots. Based on the extracted values of Jnr, the Shockley–Read–Hall lifetime of GaN p+n diodes on M‐3D and VAS substrates, τSRHM‐3Dand τSRHVAS are, respectively, estimated to be 11 and 2 ns. Under the assumption of high excitation for the 2PPL measurement, the use of τSRHM‐3D of 11 ns reproduces the 2PPL data with the effective dislocation radius ranging from 0.2 to 2 nm. The reported limitation on the on‐resistance of GaN p+n diodes is mainly validated based on bulk nonradiative recombination current densities determined from the y intercept of forward‐current density/inverse of anode radius plots of diodes on maskless 3D (M‐3D; dislocation density Ndis ≤ 4 × 105 cm−2) and void‐assisted separation (VAS; Ndis = 1–4 × 106 cm−2) substrates.