In this work, we study the internal quantum efficiency and the lasing threshold of AlGaN/GaN heterostructures designed for UV laser emission. We discuss the effect of carrier diffusion and carrier localization in the optical properties at low and room temperature. The implementation of a graded-index separate confinement heterostructure results in enhanced carrier collection, reducing the lasing threshold. However, this improvement is not correlated with the internal quantum efficiency of the samples.
Recently, there has been an increased interest in germicidal ultraviolet (GUV) lamps for disinfection. Despite extensive studies on GUV LEDs, their efficiency and cost per Watt is still far from that of mercury lamps due to electrical injection issues, among others. Also, the fact that 254 nm radiation is highly carcinogenic and cataractogenic, has motivated research on radiation with shorter penetration (200-230 nm) depth, for non-invasive disinfection.
In this study, we propose electron pumped UV lamps as an alternative to LEDs (to tackle electrical issues) in the spectral range 230-330 targeting both wavelength ranges of disinfection and exhibiting IQE ranging from 20%-50%.
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.
There is a soaring demand for UV lamps emitting at 220-270 nm for applications in disinfection. These needs are currently met by mercury lamps, hazardous for heath and the environment. Despite intense studies on UV LEDs, their efficiency remains limited by problems related to electrical injection. Here, we propose electron pumped UV lamps as an alternative to LEDs in this spectral range. For this purpose, superlattices of close-packed self-assembled AlGaN quantum dots are particularly promising, due to their high internal quantum efficiency (around 50%) and promising external quantum efficiency (4% in as-grown material, increasing to 7% by dice polishing).
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.