The authors report on room temperature (RT) lasing action in two different types of nitride-based microcavities (MCs):
vertical cavity surface emitting lasers (VCSELs) and polariton lasers which operate in the weak and in the strong
coupling regime, respectively. Following a brief description of these two operating regimes, an analysis of lasing action
at RT is reported for a crack-free planar VCSEL structure based on a bottom lattice-matched AlInN/GaN distributed
Bragg reflector (DBR) and a top dielectric DBR. The cavity region, formed by n- and p-type GaN layers surrounding
only three InGaN/GaN quantum wells, corresponds to a typical active region suitable for an electrically driven VCSEL.
Processing issues of such planar VCSEL structures and electroluminescence characteristics of processed devices are also
reported. Then, an alternative approach relying on the realization of coherent GaN-MC light sources based on the
spontaneous decay of a macroscopic polariton population, the so-called polariton laser, is described. It is shown that this
kind of devices could work at RT with a potentially much lower threshold current density than VCSELs as it does not
necessitate reaching population inversion conditions. As for VCSELs, we demonstrate laser-like properties above
threshold, i.e. an intense polarized emission and a strong spectral narrowing. Differences of polariton lasers with
conventional lasers are also highlighted.