Persons

The production of ohmic contacts to heterobipolar nanostructures has a number of peculiarities. In addition to the basic requirement of minimizing the contact resistance, the contacts to this type of structures have a transient layer, the penetration depth of which should not exceed the emitter layer thickness, otherwise the short-circuit of the emitter-base p - n -junction is possible. We have examined the influence of the main technological parameters of annealing on contact characteristics. As a result, optimization of the low-resistance ohmic contact to heterobipolar transistor layers obtaining process has been carried out. The ohmic contacts to the n -layers of heterobipolar nanoheterostructures based on gallium arsenide, obtained by the layer-by-layer electron-beam deposition of Ge/Au/Ni/Au, have been investigated. The diffusion profiles of the Ge impurity doping distribution as a function of time and the temperature of RTA have been calculated and SEM investigated. It has been determined that RTA for 60 sec at temperature of 398 °C makes it possible to obtain the ohmic contacts with low resistance, smooth morphology of the surface and the minimum size of the transition layer.

• Counter: 3399 | Comments : 0

For most commonly used semiconductor materials the contact metal systems, giving low-resistance ohmic contacts and their formation methods are known and investigated. For the materials, relatively recently applied for serial production of semiconductor devices, particularly for silicon carbide, the task of producing low-resistance ohmic devices, in spite of a significant quantity of experimental data remains an urgent one. For this purpose the works directed at production of the ohmic contacts to silicon carbide with the improved operation characteristics were carried out and are conducted. In the work the influence of the metallization composition (Ni and TiAl) the influence of the metallization composition (Ni and TiAl), the annealing process parameters, the doping of the silicon carbide contact layer by nitrogen N ions, as well as the crystallographic face (Si or C) on the resistance of ohmic contacts to 6H-SiC has been considered. It has been found that the most important influence on the process of forming the ohmic contacts to n-6H-SiC has the annealing process, as a result of which the contact resistance becomes approximately 6 times reduced. The process of contact layer doping is the second in importance. This process can reduce the contact resistance on the average by 4 times. As a result of the study it has been established that the low-resistance contacts can be obtained on both surfaces with approximately equal low resistances. The TiAl metallization is the most optimal for the C surface and Ni for the Si surface. This makes it possible to obtain the ohmic contacts on both polar surfaces with approximately the same resistances, equal to 2,5·10 Ohm·cm.

• Counter: 1896 | Comments : 0