Comparison of Au contacts to Si, GaAs, In xGa 1 − xP, and ZnSe measured by ballistic electron emission microscopy

Abstract

Ballistic electron emission microscopy (BEEM) measurements have been made on Au contacts to Si, GaAs, In x Ga 1 − x P, and ZnSe. For each semiconductor studied, a distribution of barrier heights (BHs) was observed. The distributions were compared with the current—voltage ( I/V) and capacitance—voltage ( C/V) characteristics of each metal/semiconductor contact. The BH distributions increase in width with increasing doping and/or complexity of the substrate. The effect of discrete, ionized dopants in the depletion region is considered as one source of BH distribution widening. Average BEEM measurements agree well with the BH computed from I/V and C/V measurements for all diodes if the effects of thermionic field emission and image force lowering are considered. These results demonstrate the unique application of BEEM for the nanoscale evaluation of semiconductor interface inhomogeneities critical to the control of macroscopic electronic properties.