Doping inorganic wide-bandgap semiconductors for future energy devices
EMSL Project ID
25665
Abstract
Solid-state lighting (SSL) has a significantly higher efficiency of converting electricity to visible light compared to the incandescent (5%) or fluorescent (20%) lighting due to elimination of indirect processes (production of heat or plasmas). There is no known fundamental physical barrier for SSL to achieve 100% efficiency. Currently, there are major challenges to achieve the perfect efficiency, low cost and color quality for general illumination, as identified at the workshop [1] sponsored by the Office of Basic Energy Sciences. Unlike traditional lamps, the light-emitting diode (LED) based SSL emits a single wavelength that is determined by the bandgap energy of the semiconductor material. In order to achieve different colors and mix them (e.g., blue, green and red) into white light perceived by human eye, different band structures need to be engineered. InGaN alloy system is one of the most studied materials for SSL to date because of its remarkable development of LEDs. It has been reported that the bandgap energy in the alloys decreases monotonically with increasing In contents; the emission efficiency decreases significantly at green and longer wavelengths and at high current intensities [2]. Achieving high-efficiency emission across the entire visible region is currently a challenge. Comparatively, AlN has been less studied for LEDs. It was predicted that achieving n-type doping in AlN was difficult because the material has a small bulk-intrinsic electron affinity [3]. A recent study [4] has demonstrated the success in Si doped AlN based on low-pressure metal organic vapor phase epitaxy. In this proposed work, ion-implantation method will be explored as a means to dope inorganic wide-gap materials. A fundamental investigation of the band structures and emission efficiencies as a function of material composition, structure, dopant species, concentration, defects, etc. will be performed. Understanding of the band structures is also important to improve the efficiency of solar-light absorption in photovoltaic devices.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2007-05-31
End Date
2009-09-30
Status
Closed
Released Data Link
Team
Principal Investigator