Gas-Surface Interactions on InP Monitored by Changes in Substrate Electronic Properties.

The electronic properties of compensated InP crystals can be used to sensitively monitor gas-surface interactions. When a gas is adsorbed on these low carrier density semiconductors both the conductance and minority carrier lifetime exhibit large changes which we interpret in terms of band bending. Changes of greater than 50% in the bulk-averaged conductance of Fe-compensated semi-insulating InP crystals have been measured for adsorption of ~ 0.5 monolayers of Cl sub 2. Using modulated NO sub 2 molecular beams the conductance changes are demonstrated to be fast (1 msec to steady state) so as to be capable of yielding quantative rate information about the gas-surface interaction.