Influence of metallic spikes and non-uniform density of two-dimensional electron gas (2DEG) on the contact resistance to AlGaAs/GaAs heterostructures

An expression for the series resistance of an HEMT has been derived, taking into account for the first time the nonuniformity of the ohmic contact interface. The penetration of the AuGeNi metallization into the 2DEG in the subcontract area (in the form deep penetrating “spikes”) has been investigated and the model has been elaborated in order to determine the correct value of the contact resistance depending on the fraction of the area of penetration. Simulation of the growth of the spikes depending on the thermal processes has been made. The prediction of the shape “spikes” and their density makes it possible to calculate the value of the area of penetration. Therefore, a correlation between the dependence has been experimentally verified and it gave good agreement with the model. It has established the optimum parameters of thermal processing to obtain the minimum value of series resistance. The model of nonuniformity of interface may also be used to solve the problem of the influence of a periodic electrical potential on ballistic transport in mesoscopic devices