Stimulated emission in heavily doped Al0.68Ga0.32N:Si structures with external cavity

Abstract

Room temperature broad-band stimulated emission with transverse optically pumping was demonstrated from heavily doped Al0.68Ga0.32N:Si structures with external selective and non-selective cavities. The Al0.68Ga0.3N:Si films with thickness 1.2 μm were grown by molecular beam epitaxy on (0001) oriented sapphire substrates. Stimulated emission was observed in the continuous wavelength range from 400 to 650 nm under pulse optical pumping of the YAG:Nd3+ laser with a wavelength 266 nm, 10 Hz repetition rate and 8 ns pulse width. Low optical pumping threshold power of 5 kW/cm2 at 490 nm in the external non–selective cavity has been observed. The nature of stimulated emission has been studied by means time–resolved spectroscopy. This broad band stimulated emission in the visible region is attributed with two main recombination mechanisms: slow donor–acceptor pair and fast free electron-acceptor transitions. The relative contributions of these processes are experimentally measured at all wavelength range of stimulated emission. The optical gain coefficients of (0.1–17.3) × 103 cm−1 have been determined at pump power density from 12 to 1040 kW/cm2 by direct measurement the gain of a probe radiation in the Al0.68Ga0.32N:Si structures.