Researchers at the Lawrence Berkeley National Laboratory reported that the presence of a nitrogen band formed a few tenths of an electron volt above the lowest energy conduction band in a gallium indium arsenide alloy material. Although the addition of a little nitrogen seems to decrease the alloy's bandgap and to offer the promise of more efficient conduction, it also creates a lower band that does not promote electron mobility. As a result, the electrons don't travel far enough to contribute to the output of electric current. A low-bandgap alloy could respond more efficiently to different photon energies and is promising for use in solar cells, fiber optics, detectors and light-emitting diodes. The report, published in the Feb. 8 issue of Physical Review Letters, indicates that research will now focus on how the split-band structure affects electron mobility.