Two-dimensional computer analysis of a dielectric surface-loaded GaAs bulk element

It is well established by experiment and theory that a travelling high-field domain in a GaAs bulk element is suppressed by surface loading of a dielectric material on the GaAs. To investigate this effect in more detail, a computer analysis based on a 2-dimensional model is performed. For the simulation, the full surface of a GaAs element of n = 5 × 1015cm¿3, L = 8.7 ¿m and d = 4.2 ¿m is loaded with dielectric materials of various permittivities and 0.9 ¿m thick. The cathode and anode are extended to infinity, where a linear potential distribution is assumed. The results are summarised as follows: (a) Space charges in GaAs are accumulated near the boundary between GaAs and the dielectric material, and consequently the electric field from the space charges leaks into the dielectric material. (b) As a result, the growth of a high-field domain is suppressed, and no cyclic generation of the domain occurs, if the relative permittivity of the dielectric material is 500 or more. (c) A static voltage/current characteristic of the GaAs bulk element, loaded with a dielectric material of relative permittivity 10 000, shows a current saturation. (d) All results of the present computer simulation show a qualitative agreement with the reported experiments.