SPACE-CHARGE-LIMITED BALLISTIC TRANSPORT OF ELECTRONS WITH COMPLEX DISPERSION-RELATIONS

A ballistic electron current limited by the space charge of electrons injected by the cathode in a diode with a doped base is analyzed. It i s assumed that part of the base is quasineutral as the result of quasi equilibrium electrons arriving from and returning to the anode. When t he dispersion relations for these electrons, epsilon(k), are complex a nd contain regions of negative effective masses, descending branches a rise on the plot of the current versus the voltage. Steady-state solut ions of the problem in a given class of solutions can be found only on the ascending branches of the characteristics. They do not exist on t he descending branches. Possibilities for arranging these complex disp ersion relations epsilon(k) with the help of superlattices of single o r double quantum wells are discussed. These wells would be made from m aterials whose effective masses are greatly different.