Internal-photoemission Microscopy (IPEM): Microscopic Characterization Technique for Buried Thick-metal/Semiconductor Interfaces

摘要

We have developed internal-photoemission microscopy (IPEM) which is capable of revealing microscopic inhomogeneity in SBH's at thick-metal/semiconductor interfaces, which had not been disclosed by the conventional current-voltage (Ⅰ-Ⅴ) or capacitance-voltage (C-V) techniques. Inhomogeneous degradation of Ti/Pt/Au contacts to GaAs was shown by using this technique. In this experiment, the IPEM results revealed that local formation of an Au-Ga alloy is responsible for the degradation of macroscopic Ⅰ-Ⅴ characteristics of the diodes. SBH inhomogeneity at epitaxial-Al/Si(111) interfaces was clearly observed after annealing at temperatures 450-550℃. I discussed the discrepancy between SBH values determined by the Ⅰ-Ⅴ and C-V methods in relation to microscopic IPEM images of several stages of annealing. IPEM can apply to optimization of multilayered semiconductor contacts. It has been shown that the combination between IPEM and the test sample with a tapered first Ni-layer as well as an Al-layer is an effective way of optimizing Al/Ni/Al-InP Schottky contacts.