Relaxation Processes in Submicron Heterotransistors with a System of Quantum Wells

Abstract

The analysis of relaxation processes in submicrometer heterostructure transistors with the system of quantum walls is investigated. The methods of nano heterostructure design are developed including quantum effects and specific for ternary alloys scattering mechanism. Modeling based on the relaxation equations system for submicrometer heterostructures with quantum walls is fulfilled.The optical, acoustic, intervalley and doping scattering mechanisms is considered. New approach allows to study the influence of alloy scattering as well as. The relaxation times are expected for scattering mechanisms and the influence on field-speed and output characteristics of submicrometer heterostructure transistor are estimated.The modeling results take into account influence of casual fluctuations of the molar concentration of aluminium in the structure of transistor. The analysis of the scattering mechanisms is considered in the 2D-model of structure, that allows to estimate influence of the separate scattering mechanisms on the electronic gas in heterostructures with the systems of quantum walls. Polar optical phonons scattering is basic in such structures, while in an area gate-drain does not begin to prevail the intervalley scattering mechanism.It is shown that the average drift speed in the heterotransistor with two channel structure are more high, than in heterotransistor with one potential wall and two heterojunctions transistors have higher values of output current.The growth of the average drift speed in a structure with two quantum walls in comparison from heterotransistor with one quantum walls makes to 30-40%. It is related to the redistribution of electrons between potential walls with the loss of the energy at overcoming of barriers.The modeling results shown that warming-up of electronic gas and growth of the electrons temperature is a greater degree related to the electrons which drift in potential walls at heterojunctions.It is also necessary to take into account the dimensional quantization effect. This effect in heterostructure is require the calculation of discrete energy levels in quantum walls.Diminishing of the influence of strong electric-field effects in a two channel structure is related to the diminishing of scattering probability both on polar optical phonons and as a result of the injecting of electrons to lower heterojunction with high initial speed and small values of energy which diminishes also probability of the intervalley scattering.The model of calculation of the quantum walls influence on the longitudinal transport in the heterojunction transistors with submicrometer gate length are developed. The mathematical model can be used for the calculation of not only heterostructures transistor but also other constructions of multi-layered devices with the systems of quantum walls in the conditions of the strong electric fields.Ref. 13, fig. 19.