Parameters of stimulated emission in Al$_{0.65}$Ga$_{0.35}$N : Si/AlN/Al$_2$O$_3$ structure with planar geometry

The parameters of stimulated emission from the Al$_{0.65}$Ga$_{0.35}$N : Si/AlN/Al$_2$O$_3$ heterostructure were experimentally studied in the wide spectral range of 370–670 nm at room temperature, caused by the action of transverse pulsed optical pumping with the wavelength radiation of 266 nm, pulse duration of 8 ns, and the repetition rate of the 10 Hz. The silicon doped Al$_{0.65}$Ga$_{0.35}$N film of the concentration $n_{\mathrm{Si}}\approx$1.5 $\cdot$ 10$^{20}$ cm$^{-3}$, with a thickness of 1.1 mkm is the asymmetric planar with the optical gain of $\sim$10 cm$^{-1}$. The quantum efficiency of stimulated emission is $\eta\approx$18% at the optical pumping power of the 100 kW/cm$^2$ and the output of stimulated emission through the Al$_2$O$_3$ substrate. The emission spectrum consists of a set of equidistant peaks, each of which consists of the sum of two plane TE and TM waves. These waves propagate in a zigzag manner due to internal reflection at the boundaries of the structure. A narrow angular divergence of 5.3$^\circ$ of stimulated emission in the direction perpendicular to the plane of the structure is obtained, and the parallel direction divergence is 20$^\circ$.