Department of Materials Science & Engineering
NC State Unviersity
Challenges and breakthroughs in the development of AlGaN-based UVC lasers
Location: EB1 Room 1011
Friday, September 16th 2016 - 11:00 am
Despite the rapid progress in III-nitride-based laser diodes, sub-300 nm UV semiconductors lasers have not been realized yet, mainly due to technical and scientific barriers arising from the lack of proper crystalline substrates and poor understanding of defect control in the wide bandgap semiconductors. Al-rich AlGaN alloys are the building blocks for these deep UV optoelectronics devices and it has been demonstrated that the highest crystalline quality Al-rich AlGaN films are obtained on AlN single crystal substrates. In addition to low dislocation density, reduction in non-radiative centers and compensating point defect is required to achieve high internal quantum efficiency. Recently, UV LEDs emitting at 265 nm with output powers exceeding 80 mW and high reliability, as well as low-threshold, optically pumped lasers emitting at wavelengths between 230-280 nm that display cavity modes and single polarized-state emission have been demonstrated. Nevertheless, there are still several issues related to the performance and further improvement of the heterostructure-based active regions as related to their quantum efficiencies and the polarization of their emission is desired. These issues to be discussed are classified in two main categories: (1) growth, crystallography and surface morphology control and (2) identification and control of point defects. In addition to this, results on electrically-pump laser structures will be discussed, showing the very near possibility of the first ever demonstration of deep UV semiconductor lasers. Such devices will find direct and immediate uses in health care, bio-defense and other commercial and defense applications. The use of light sources in the deep UV will lead to detection systems of different chemical and biological aerosols, providing for detection of a variety of pollutant agents among other effluents, in addition to help in increasing the availability of clean potable water through efficient UV disinfection.