Inter-Conduction-Band Transitions in the Electroreflectance Spectrum of InSb

Band-population effects in the surface region of semiconductors facilitate identification of parts of their electroreflectance spectrum. Structure exhibiting a red, a blue, or no shift in response to an increase of the surface potential corresponds to transitions starting from, ending at, or bridging the Fermi level. Using this criterion in n-type InSb, structure at 3.1 and 3.5 eV, which shows a red-shift, is assigned to transitions from the populated lowest conduction band Γ6c to the next-higher bands Γ7c and Γ8c. In addition, these observations, as well as the observation of complementary structure which we assign to valence-to-conduction-band transitions at or near the Γ point, give the separation between Γ₈ᵥ and Γ7c as 3.4 eV.