Low-Temperature-Grown GaAs LED Emits at 1550 nm

By introducing arsenic antisite deep levels into a GaAs lattice, researchers at Yale University in New Haven, Conn., have coaxed telecom-friendly 1550-nm radiation from a GaAs LED. The work promises to ease the development of advanced devices for telecommunications applications.

Janet L. Pan, a professor of electrical engineering and applied physics at the university, explained that GaAs is the most established technology for the production of inexpensive integrated optoelectronics, but its bandgap wavelength of 850 nm makes it unsuitable for use with long-distance fiber optic communications. The researchers therefore sought to create artificial deep-level energy bands in GaAs that would lead the material to emit radiation at a more suitable wavelength.

To do so, Pan's team employed low-temperature molecular beam epitaxy to grow a 400-nm-thick layer of GaAs with arsenic antisites -- defects in which an arsenic atom replaces a gallium atom in the crystal lattice -- between layers of doped and undoped GaAs. An LED fabricated with the technique displayed room-temperature electroluminescence at wavelengths of 1400 to 1700 nm with a peak at approximately 1550 nm, an estimated internal optical power of 24 mW and a 200-fs below-threshold total relaxation rate that suggests the potential for terahertz speeds.

Pan is cautiously optimistic about the work, noting that much engineering will be required to extract the internal optical power; the estimated external power in the demonstration was 560 µW. She said, however, that increasing the 0.6 percent efficiency and lowering the operating currents might enable the realization of practical devices within three to five years.

An advance report of the device appeared in the online edition of Nature Materials on May 4.