Thermally-annealed InGaN quantum wells (QWs) with various interdiffusion lengths (L
) are numerically analyzed as improved active region for Light-Emitting Diodes (LEDs). The calculations of the band structure, wavefunction for electrons and holes are based on a self-consistent 6-band k·p method taking into account the valence band mixing, strain effect, spontaneous and piezoelectric polarizations and carrier screening effect. The spontaneous emission radiative recombination rate (R
) was calculated for thermally-annealed 3-nm In
N QWs with various interdiffusion lengths (L
), as compared to that of the conventional InGaN QWs emitting at the similar wavelength. Studies show that the electron-hole wavefunction overlap is significantly enhanced for the thermally-annealed InGaN QWs, which results in the improved spontaneous emission radiative recombination rate for enhancing LED output power.