Direction reversal of the surface band bending in GaAs-based dilute nitride epitaxial layers investigated by polarity of terahertz electromagnetic waves

We have investigated the polarity of terahertz (THz) electromagnetic waves from GaAs-based dilute nitride (GaAs1−xNx and InyGa1−yAs1−xNx) epitaxial layers to clarify the effects of nitrogen incorporation on the direction of the surface band bending. The THz-wave polarities of the dilute nitride samples are reversed compared with those of an i-GaAs/n-GaAs sample that has an upward surface band bending; namely, the dilute nitride samples have a downward band bending. The polarity reversal is attributed to the phenomenon that the conduction band bottom is lowered by the band anticrossing due to the nitrogen incorporation, which changes the direction of the band bending.