Lateral inhomogeneities in engineered Schottky barriers

We have measured the lateral homogeneity in Al/GaAs(0 0 1) Schottky barrier s engineered for low barrier height through fabrication of a Si layer at th e interface under As flux. We used a spectroscopic photo emission and low-e nergy electron microscope (SPELEEM) which combines a low-energy electron mi croscope with an imaging band pass filter to allow spatially resolved synch rotron radiation photoemission experiments. As-grown samples with a Si inte rlayer thickness of 0.5 and 3 monolayers appeared homogeneous within the sp atial resolution of the SPELEEM (22 nm). Annealing an Al/Si(As)/GaAs(0 0 1) heterostructure for 10 min at 500 degrees C, however, caused inhomogeneous As outdiffusion which is correlated with a local As 3d core level shift of 0.3 eV. We suggest that the reported degradation of such engineered Schott ky barriers might be correlated with laterally inhomogeneous As out-diffusi on upon annealing. (C) 1999 Elsevier Science B.V. All rights reserved.