Fabrication of semipolar AlGaN UV LEDs on sapphire substrates

Semipolar III-nitride semiconductors have attracted much attention due to their superior optical properties.[ 1 – 4 ] In terms of structural polarization along the growth direction, reduced polarization field in semipolar orientations can relieve the quantum confined Stark effect in quantum wells (QWs) compared to a (0001) orientation, increasing the radiative recombination rate of electron-hole pairs in the QW. In terms of optical polarization of the emitted light, semipolar orientations would generate a TE-polarized light for the entire Al compositional range in AlGaN, which is suitable for shorter-wavelength emitters. Thus, semipolar AlGaN has many advantages for deep-UV emitters.