Negative band gaps in dilute InNxSb1-x alloys.

A thin layer of InNSb has been fabricated by low energy nitrogen implantation in the near-surface region of InSb. X-ray photoelectron spectroscopy indicates that nitrogen occupies approximately 6% of the anion lattice sites. High-resolution electron-energy-loss spectroscopy of the conduction band electron plasma reveals the absence of a depletion layer for this alloy, thus indicating that the Fermi level is located below the valence band maximum (VBM). The plasma frequency for this alloy combined with the semiconductor statistics indicates that the Fermi level is located above the conduction band minimum (CBM). Consequently, the CBM is located below the VBM, indicating a negative band gap material has been formed. These measurements are consistent with k.p calculations for InN0.06Sb0.94 that predict a semimetallic band structure.