Warm electron effects in GaAs at low temperatures

The field impact ionization of shallow donors in n-type GaAs at low temperatures gives rise to non-ohmic conduction effects. This has been observed in both vapour and liquid phase grown epitaxial GaAs at temperatures between 4.2 K and 20 K. At fields greater than 10 V cm -1 the complete ionization of the donors gives a known carrier concentration which allows the electron mobility as a function of electric field to be investigated. The results have been interpreted in terms of polar mode scattering, being the dominant energy loss process for fields greater than 10 V cm -1 , and ionized impurity scattering, being the mobility limiting process. Excellent qualitative and quantitative agreement has been obtained between the experimental and theoretical mobilities.