III-Nitride: Reaching for longer and shorter wavelengths


The application of III-Nitride materials to semiconductor light emitters is suddenly extending to a wider wavelength range. The long wavelength limit at the InN bandgap was previously thought to correspond to 1.9eV, while our recent work shows that the InN bandgap is actually near 0.7eV. This surprising discovery is the result of characterization of InN, grown by molecular beam epitaxy (MBE), which exhibits significantly higher crystalline perfection and purity compared to past techniques. The growth and characterization techniques that led to this conclusion will be presented. New InN applications include light emitters, solar cells and transistors.

Even longer wavelength emission is sought through intersubband emission from confined states in the conduction band of III-Nitride quantum wells. Optical absorption at wavelengths out to 5 microns in a GaN single quantum well has been observed. Intersubband absorption at wavelengths as short as 1.1 microns opens the door to high speed, high power operation at telecom and mid-IR wavelengths

Short wavelength light emission from III-Nitrides is receiving strong attention. Interest in III-V nitride semiconductor materials has intensified with the search for low cost, compact and efficient UV light sources. Many new techniques for detecting and eliminating hazardous substances will require battery operated generation of light at wavelengths as short as 280nm. Secure communications are enabled at wavelengths below 260nm. The challenge to the semiconductor community is to create n- and p-type AlGaN that significantly reduces the resistivity of these materials and their contacts.