Electrical measurements on n⁺-GaAs-undoped Ga _0.6Al_0.4 As-n-GaAs capacitors

Current versus voltage (I-V) and capacitance versus voltage (C-V) characteristics have been measured for n+-GaAs-undoped Ga 0.6Al0.4 As-GaAs capacitors over a temperature range of 80-350 K. At low temperatures the structure behaves like a semiconductor- insulator-semiconductor diode with interface barrier heights of 0.38 and 0.40 eV for the bottom and top interfaces, respectively. The I-V curves exhibit a rectifying behavior due to the formation of a substrate depletion layer, and the C-V curves show the formation of the depletion layer under reverse bias as well as an accumulation layer containing >1012 electrons/cm2, in forward bias. The C-V curves agree closely with standard theory for SIS structures assuming Fermi-Dirac statistics for electrons in the accumulation layer, within an unaccounted-for voltage shift of 0.16 V.