Surface photovoltage spectroscopy with cleaved GaAs (110) surfaces: Spectroscopy of Cr2+

Surface photovoltage spectra of clean (110) surfaces cleaved from n‐type GaAs crystals doped with Te or Si exhibit two narrow peaks at 0.72 and 0.89 eV superimposed on a broad shoulder extending from h/ω≊0.7 eV to Eg. Both peaks are strongly increased by chemisorption of oxygen and by increasing the band bending. The peak at 0.89 eV is attributed to intra‐ion 3d transitions of deep Cr2+ impurities, with the ground state 0.72 eV below the conduction band edge. The presence of chromium in the samples was proven by AES after anneals at 800 K, causing an enrichment of chromium near to the surface. The growth of the 0.89 eV peak proportional to the square of the surface potential is explained by an increase of the net escape probability from the excited state into the conduction band via tunneling.