A methodology is presented for altering the electrical properties of contacts to III–V compound semiconductors through the use of controlled interfacial chemical reactions. The process by which this is accomplished has been termed the exchange mechanism. Under this mechanism, a metallization consisting of a transition metal and a group III element (denoted TIII′) is reacted with the semiconductor (denoted IIIV) in such a way that the group III elements of the metallization and substrate, III′ and III, are exchanged without the formation of any new phases. This leads to the creation of a ternary semiconductor alloy S, or IIIXS′III1-XSV, at the contact interface, where XS denotes the mole fraction of III′V in the semiconductor alloy phase S. The electrical properties of the contact subsequent to the exchange reaction then correspond to those of a metal/IIIXS′III1-XSV interface. Moreover, by employing ternary metallizations of varying composition M, or TIIIXM′III1-XM (where XM represents the mole fraction of TIII′ within the ternary metallic phase M), the resulting interfacial composition of the semiconductor and hence the electrical properties of the contact may be varied in a systematic fashion. Rather stringent thermodynamic and kinetic criteria must be met in order for the exchange reaction mechanism t- o be operative. These factors are described using a quantitative model. The limitations of applicability of the model are also discussed. © 1998 American Institute of Physics.