CAPACITANCE-VOLTAGE AND CURRENT-VOLTAGE CHARACTERIZATION OF ALXGA1-XAS-GAAS STRUCTURES

AlxGa1-xAs-GaAs structures with thin (400-1000 Angstrom) Cr-doped or u nintentionally doped AlxGa1-xAs layers (0.3 less than or equal to x le ss than or equal to 1) were grown on n(+) GaAs substrate by molecular- beam epitaxy. The AlxGa1-xAs-GaAs interface and the insulating propert ies of thin AlxGa1-xAs layers at 300 K have been studied by capacitanc e-voltage and current-voltage measurements, respectively. An AlxGa1-xA s-GaAs interface state density in the lower 10(9) eV(-1) cm(-2) range was obtained. The insulating properties of thin AlxGa,As-1-x layers we re found to be controlled by AlxGa1-xAs-GaAs interface band offsets (D elta E(o),Delta E(v)) and metal-AlxGa1-xAs barrier height Phi(Bn) in a ccumulation and deep depletion, respectively, rather than by AlxGa1-xA s bulk properties such as specific bulk resistivity. Furthermore, requ ired electrical properties of insulating layers employed in metal-insu lator-semiconductor structures are discussed using a self-consistent h eterostructure model based on Poisson's equation and current continuit y equations. Finally, a fundamental equation for the formation of inve rsion channels has been derived. (C) 1995 American Institute of Physic s.