Deep-UV Optical Emitters based on GaN/AlN quantum structures

Abstract

Light-weight and robust ultraviolet (UV) light emitting sources find potential applications in water purification, bio sensors, solid state lighting and lithography.  Direct-bandgap III-Nitride semiconductors exhibit bandgap energies extending upto 6.2 eV (210 nm, deep UV) and are thus attractive to realize UV LEDs. But as the Al composition is increased to reach shorter wavelengths, the internal quantum efficiency (IQE) severely degrades due to as the valence band asymmetry, high threading dislocation densities, quantum-confined Stark-effect, and inefficient n- and p-type doping.  To mitigate the adverse effects of such factors and to boost the IQE, we have proposed and demonstrated a new design that incorporates ultra-small GaN quantum dots (QDs) in AlN barriers along with polarization doped p-AlGaN layers, and uses quantum mechanical tunneling to inject and transfer carriers through the active region. The novel LDE design produces emission at 240 nm and improves the UV light intensity > 20 times. The successful demonstration paves the way for efficient LEDs and laser diodes (LDs) in the short-wavelength regime, which remains an unconquered territory.