The electronic properties of undoped semihyphen;insulating GaAs were studied by measurements of current injection under a planar configuration which is sensitive to the nearhyphen;surface region. TheIhyphen;Vcharacteristics were measured as a function of temperature in the range of 295ndash;360 K for the ashyphen;received state and also following a heat treatment of 850thinsp;deg;C /20 min using a Si3N4cap. In order to understand the observed characteristics, a computer program was developed to simulate the current both in the ohmic and spacehyphen;chargehyphen;limited regimes. The combination of the electrical measurements and simulation enabled the determination of the parameters controlling the resistivity of the semihyphen;insulating samples, and shed light on the trap distributions and concentrations. It was found that the normally assumed threehyphen;level compensation model is inadequate to explain the observed behavior. Two other deep donors lying at 0.56 and 0.40 eV below the conduction band are suggested by the data (in addition to EL2); these two donor levels control the resistivity. In some instances, the influence of a deep acceptor is also observed.
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