Carrier-transport processes in $n^{+}$-GaAs/$n^{0}$-GaAs/$n^{+}$-GaAs isotype heterostructures with a thin wide-gap AlGaAs barrier

Experimental studies of $n^{+}$-GaAs/$n^{0}$-GaAs/$n^{+}$-GaAs isotype heterostructures with a 100-nm-thick wide-gap $N^0$-AlGaAs barrier situated in the $n^0$-GaAs region are carried out. It is shown that the current–voltage characteristic of the structures under study has a negative-differential-resistance (NDR) portion, with the transition to this region occurring with a time delay that may reach tens of nanoseconds. It is found that operation in the NDR region is associated with the onset of impact-ionization process. Numerical analysis in terms of the energy-balance model demonstrated that the transition to the NDR region is associated with the formation of an electric field domain that covers a part of the lightly doped region between the thin wide-gap $N^0$-AlGaAs barrier and the heavily doped $n^+$-GaAs layer and with the onset of impact ionization at the interface with the heavily doped $n^+$-GaAs layer. A comparative analysis of the experimental data and the modeling results showed that, for the current–voltage characteristics of the heterostructures under study to be correctly described, the model should take into account the less pronounced ability of a heterojunction to restrict carrier transport in the barrier layer.