The interface transport properties of Ge-GaAs heterojunctions

The interface conductance of Ge-GaAs heterojunctions has been measured as a function of junction field up to 1.2 × 105 V/cm. It is seen that for samples with surface mobility of about 500 cm2/V · sec, the mobility μ8 varies with field, at most, as E-0.1 up to about 8 × 104 {v/cm}, but for higher fields it varies approximately as E-0.35. Measurements have been made also of junctions whose properties are affected by the proximity of a free surface and junctions which have been heat-treated at 600° C ∼ 650° C. A comparison of these results with those of normal heterojunctions is seen to lend further support to the Shockley-Anderson model for abrupt heterojunctions. Namely, in terms of interface states, normal heterojunctions have no detectable interface state densities within the present experimental errors (< 5 × 1010/cm2), while some heat-treated junctions have acceptor type interface state densities of more than a few times 1011/cm2. © 1964.