Metal-semiconductor contacts and semiconductor heterojunctions are wellestablished concepts in semiconductor device technology. The key parameters characterizing such junctions are the barrier height and valence band discontinuity at the interface and the electronic interface states. Clean cleaved GaAs(110) surfaces exhibit no intrinsic surface states in the bulk band gap but do exhibit extrinsic cleavage-induced states. Furthermore, local segregates of arsenic were detected. The chemisorption of metals, semiconductors, hydrogen and oxygen causes depletion layers to form on both n-and p-type crystals. The surface states responsible for these band bendings, which persist even under thick layers of metals and semiconductors, are thought to be related to chemisorption-induced defects. Possible candidates are discussed. Chemical trends are also considered.
Semiconductor Device Technology
