ON THE ACCUMULATION CAPACITANCE OF SI3N-4/SI/GAAS STRUCTURES FABRICATED IN AN ELECTRON-CYCLOTRON-RESONANCE PLASMA

Investigations of the Si3N4/Si/GaAs capacitor were carried out. In comparison with a structure without the Si interlayer the interface state density in the mid-gap region is remarkably reduced; it was estimated to be of the order of approximately 7 x 10(11) eV-1 cm-2. On the basis of the Q-DLTS measurements where a peak with an anomalous behavior has appeared, a qualitative model for the existence of a quantum well is proposed. The well is suggested to prevent the Fermi level at the semiconductor surface from approaching the GaAs conduction band. Our data suggest that a space-charge region at the GaAs surface exists also in strong accumulation, which lowers the true accumulation capacitance.