Photoluminescence (PL) and stimulated emission of GaN/Si layers grown by MOVPE with AlN and AlGaN buffers have been investigated. It has been found that thermal annealing of samples in nitrogen gas flow leads to an increase of the PL efficiency of up to 20 times, with a thermal activation energy of this process of 3.1–3.4 eV. The annealing promotes a significant decrease of the non‐radiative center concentration and an increase of the number of shallow states. The laser action at λ = 377 nm under pulsed optical excitation was achieved at room temperature evidencing a high quality of the samples.
The violet-green laser converter based on a molecular-beamepitaxy (MBE) grown CdSe quantum dot (QD) laser heterostructure pumped by a commercial InGaN laser diode (LD) emission has been fabricated and studied in detail. The optimized II-VI laser heterostructure consists of asymmetrical ZnSe/ZnSSe superlattice (SL) waveguide and active region comprising five CdSe QD sheets (QDS) placed in the centre of 2-nm-thick ZnSe quantum wells. The new laser structure design provides both a high homogeneity of optical pumping of the CdSe QDS due to tunnelling of charge carriers between the QDS separated by 5-nm-thick ZnSe/ZnSSe/ZnSe barriers and high optical confinement factor. Optimization of both cavity length of the II-VI laser and parameters of optical focusing system to obtain a narrow stripe with the length slightly exceeding the cavity length has been performed. As a result, the maximum achieved quantum efficiency and pulse output power in green have been as high as 8% and 65 mW, respectively.
Optically pumped lasing in the wavelength range of 450–470 nm in InGaN/GaN multiple-quantum-well heterostructures grown by metalorganic vapor phase epitaxy was achieved and investigated. The energy and power per pulse of the laser were 80 nJ and 10 W correspondingly for one facet at room temperature. The far-field patterns of the laser emission consisted of three light spots near the angles of +30°, −15°, and −45°. The highest operating temperature was 450 K. The photoluminescence and photoluminescence excitation spectrum structures suggest that the quantum dots inside the quantum wells are involved in the recombination mechanism.
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