Aluminum Nitride Deep-Ultraviolet Light-Emitting Diodes

By Yoshitaka Taniyasu, Makoto Kasu, and Toshiki Makimoto, NTT Science and Core Technology Laboratory Group

Abstract

We have successfully fabricated an aluminum nitride light-emitting diode (LED) and observed ultraviolet light with a wavelength of 210 nm. This is the shortest wavelength ever observed from any semiconductor. This LED represents a major step towards replacing large, toxic, and low-efficiency gas light sources with compact, harmless, and high-efficiency semiconductor light sources. The application fields of these LEDs include environmental protection, nanotechnology, and information technology.

Introduction

The shortest-wavelength color of light that is visible to the human eye is violet. Light with wavelengths shorter than 400 nm is called ultraviolet (UV) light: that from 300 to 400 nm is called near-UV light, that from 200 to 300 nm is called deep-UV light, and that shorter than 200 nm is called vacuum-UV light. Since vacuum-UV is absorbed by air, deep-UV light is the shortest wavelength that can be used in our living environment.

The deep-UV light sources available at present are gas light sources, such as mercury lamps or gas lasers. These contain toxic substances, which cause serious environmental problems. Moreover, gas lasers require frequent supplies of gas and are large and inefficient. Therefore, replacing these gas light sources with semiconductor light-emitting devices, such as light-emitting diodes (LEDs) and laser diodes (LDs), would save space and greatly improve reliability and efficiency. In addition, semiconductor devices are durable and portable. These features will be advantageous for a variety of new applications.