Slipokurov V. Development of testing methods for parameters of Pd–Ti–Au ohmic contacts to silicon microwave diodes

The thesis deals with development of testing methods for parameters of ohmic contacts to the n+-Si and n+-n-n+-Si semiconductor structures that are widely used in power silicon microelectronics. A model of the effect of ohmic contact parameters on the output power of IMPATT diode has been developed in the thesis. Based on this model, the requirements to ohmic contacts of silicon IMPATT diodes operating in the millimeter and submillimeter frequency ranges have been formulated and the contact metallization layers have been selected. The method has been proposed to reduce error when determining the contact resistivity from an analysis of statistical distributions of contact resistivity and surface resistivity of semiconductor. The method for investigation of ohmic contacts to multilayer semiconductor structures has been developed. Both temperature dependence of Au–Ti–Pd–n+-n-n+-Si contact resistivity and mechanism of current flow in these contacts have been investigated. Contrary to the known results for similar layered structure, it has been obtained the decreasing temperature dependence rather than the increasing one of contact resistivity. It is related with the more optimum thickness of the palladium layer. The method for investigation of heat resistance of IMPATT diodes has been developed. This method is more informative than the standard one. In addition, the effect of heat resistance between IMPATT diode and heat sink is removed. A method for rejecting potentially unreliable IMPATT diodes by parameters related to heat resistance and series-loss resistance is developed.