Angle-resolved photoemission spectroscopy (ARPES) was used to characterize the surface state of clean CdZnTe (I 10) surface. The surface state of CdZnTe with the peak at 0.9 eV below the Fermi level is identified. Meanwhile, Photoluminescence (PL) spectrum confirmed that there existed a surface trap state which introduced a deep-level peak at 1.510 eV. The surface trap states can be decreased by aging in dry-air. The surface leakage current was measured also by I-V measurements. After aging, the leakage current was decreased remarkably, which suggested that the aging treatment is an effective method to decrease the surface trap state. (c) 2005 Published by Elsevier B.V.