A comparison of minority electron transport in In0.53Ga0.47As and GaAs

The electron transport properties of heavily doped p-type In0.53Ga0.47As and GaAs have been investigated and the applications in heterojunction bipolar transistors (HBTs) are emphasized. Using the dielectric function formalism, we have characterized minority electron transport in terms of mean-free path and diffusivity. These parameters quantify the nonequilibrium (ballistic) and near-equilibrium (diffusive) transport in the p-type base region of HBTs. Our calculations demonstrate that electron energies above 300 meV provide no benefit for ballistic transport in p-type InGaAs in terms of momentum relaxation mean-free path. Especially for very heavily doped cases (∼1020 cm−3), low-energy electron injection into the p-type InGaAs base is more advantageous for base transport, as well as the succeeding transport in the base-collector depletion region. When diffusive transport is dominant, p-type InGaAs exhibits superior performance over GaAs for a wide range of doping concentrations.