Development of magnesium zinc oxide deep ultraviolet semiconductor lasers

About This Grant

A diode laser device is made from semiconductor, a material with its electrical conductivity dictated by the quantities of negatively and positively charged mobile particles within itself, which are referred as electrons and holes, respectively. An n-type semiconductor possesses more electrons than holes while a p-type semiconductor has more holes than electrons. Traditional diode laser devices contain a key component equivalent to a p-n junction, where electrons and holes meet and recombine to emit light. Diode lasers with emission wavelengths in the infrared and visible spectral bands are widely commercially available. In contrast, those devices emitting lasing with wavelengths less than 315 nanometers in the deep ultraviolet (UV) spectral bands (UV-B and UV-C) are severely underdeveloped. This is because the material used to develop those lasers, namely aluminum gallium nitride (AlGaN), has fundamental issues including weak p- and n-type conductivities. This project addresses this challenge by developing novel metal-semiconductor-metal random laser devices based on magnesium zinc oxide (MgZnO) semiconductors. These devices use the injection of high-energy electrons from power supply to generate amplified numbers of electron-hole pairs for lasing, thus circumventing the strong p-type requirement in conventional semiconductor p-n junction lasers. The principal investigator and his students will work to achieve MgZnO lasers with deep-UV emission wavelengths between 315 and 200 nanometers. In addition, a novel approach will be used to convert random lasers which emit light with multiple wavelengths in all directions into highly directional, single-wavelength MgZnO lasers. The success of this effort will enable the development of portable semiconductor lasers in the deep-UV spectral bands for next-generation data storage and recording, medical diagnosis and surgery, photodynamic therapy, biological agent detection and sterilization, and water purification. Thus, it will have a profound positive impact on national health, prosperity and welfare. This project will train PhD students and undergraduate students who will graduate with versatile skills to advance semiconductor photonics technology in industry, academia, or government. Educational outreach will be extended to K-12 students to foster their interest in semiconductors. Additionally, the project will help train semiconductor nanotechnology technicians, a workforce increasingly in demand by society. Technical Description: This project seeks to overcome fundamental challenges to the development of deep-UV semiconductor lasers. It will demonstrate novel MgZnO deep-UV laser devices with an emission wavelength range between 200 and 315 nm in the UV-B and UV-C bands using metal-semiconductor-metal junctions rather than conventional p-n junctions. Gallium-doped n-type MgZnO nano-column semiconductor thin films with various Mg mole fractions will be grown using molecular beam epitaxy. Deep-UV metal-semiconductor-metal random lasers with scalable output power as a result of impact ionization, and their mode-coupled highly directional and single-mode lasers will be simulated, fabricated and characterized. Despite the enormous success of semiconductor lasers in all other spectral ranges including near-UV, visible, infrared and terahertz, electrically driven coherent single-mode semiconductor lasers operating at wavelengths less than 315 nm at room temperature are rare. This research will fill the 200 to 315 nm range wavelength gap, which will impact areas such as information storage, display and imaging, biology and medical therapeutics, and water purification. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.