Studies of GaAs–oxide interfaces with and without Si interlayer

We have studied the properties of metal–oxide–semiconductor structures fabricated by plasma enhanced chemical vapor deposition of SiO2 upon GaAs substrates. We have characterized the dependence of these properties upon the presence of a silicon interlayer, the type and the degree of misorientation of the substrate, and the type of plasma enhancement. We conclude that the presence of a silicon interlayer is beneficial for n‐type GaAs if the oxide is deposited by a remote plasma technique. For such oxides on n‐type GaAs coated with silicon, integration of the quasi‐static capacitance curve suggests a band‐bending range of 0.6–0.9 V. Also for these samples, we observe a hysteresis of order 0.6 V, and shifts of only 0.2 V in the midpoint of the rise from minimum to maximum capacitance upon changing frequency from 10 to 200 kHz. The benefits of using a silicon interlayer with a direct plasma deposited SiO2 film are less evident. It is assumed that much of the improvement of these results arises not from a large reduction of the interface density but rather from a shift of the spectrum towards the conduction band edge. This appears evident from the improvement on n‐type samples coincident with a degradation on p‐type samples. The total band bending change derived from the integral from the quasi‐static capcitance–voltage curves is less sensitive to this interlayer than is the frequency dispersion.