Development of AlGaN/GaN heterostructures for e-beam pumped UV lasers

Abstract

Here, we present the design and fabrication of AlGaN/GaN heterostructures that constitute the active element of electron-beam pumped UV lasers. The design of multi-quantum-well separate confinement heterostructures (SCHs) and graded-index separate confinement heterostructures (GRINSCHs) was adapted based on Monte Carlo simulations of the electron penetration depth. The structures were synthesized by plasma-assisted molecular beam epitaxy on bulk GaN substrates, and validated using transmission electron microscopy and X-ray diffraction. Mirror facets were fabricated by cleaving. Cathodoluminescence studies prove the benefits of the GRINSCH design in terms of carrier collection efficiency. The threshold power density under optical pumping with an Nd-YAG laser (266 nm) was below 200 kW/cm2 at room temperature.