The multiple color-matching schemes that could improve the color rendering index for phosphor-free white LEDs are discussed. Then we review a few of the recent research directions for phosphor-free white LEDs, which include the development of monolithic GaN-based white LEDs and hybrid integrated GaN-based and AlGaInP-based white LEDs. These development paths will pave the way toward commercial application of phosphor-free white LEDs in the coming years.

Polarization-stable 980 nm oxide-confined vertical-cavity surface-emitting lasers with 3 𝜇m diamond-shaped aperture are fabricated by comprehensively utilizing the anisotropic properties of wet etching and wet nitrogen oxidation of III-V semiconductor materials. Polarization-stable operation along the major axis of the diamond-shaped oxide aperture with 11 dB orthogonal polarization suppression ratio is achieved in a temperature range of 15-55 ∘ C from the threshold to 4 mA.