Zero-Field Time-of-Flight Measurements of Electron Diffusion in P+-GaAs

Minority electron diffusivities in p+-GaAs-doped N A≃1.4×1018 and ∼1019 cm-3 have been measured in zero-field conditions with an extension of the zero-field time-of-flight technique. Extension of the technique to make it applicable to heavily doped p+-GaAs is described and zero-field data are discussed. Unexpectedly, majority carrier drag effects are not evident in a comparison of this data with recently reported high-field data. Low zero-field mobility of electrons in p+-GaAs has important implications for high-speed devices such as heterojunction bipolar transistors.