MOLECULAR CONTROL OF A GAAS TRANSISTOR

The interactions between adsorbed organic molecules and the electronic charge carriers in specially made GaAs structures are studied by time - and wavelength-dependent measurements of the photocurrent. The adsor ption of the molecules modifies the photocurrent decay time by orders of magnitude. The effects are molecularly specific, as they depend on the electronic properties and absorption spectrum of the molecules. Th ese observations are rationalized by assuming that new surface states are created upon adsorption of the molecules and that the character of these states is controlled by the relative electronegativity of the s ubstrates and the adsorbed molecules. The relevance for surface passiv ation and for construction of semiconductor-based sensors is indicated . (C) 1998 Elsevier Science B.V.