An investigation of the Pd-In-Ge nonspiking Ohmic contact to n-GaAs using transmission line measurement, Kelvin, and Cox and Strack structures

The Pd-In-Ge nonspiking Ohmic contact to n-GaAs has been investigated using the transmission line, the Kelvin, and the Cox and Strack structures. It has been found that a layered structure of Pd/In/Pd/n-GaAs with 10-20 Å of Ge imbedded in the Pd layer adjacent to the GaAs can lead to a hybrid contact. When the Ohmic formation temperature is above 550°C, a layer of In xGa1-xAs doped with Ge is formed between the GaAs structure and the metallization. When the Ohmic formation temperature is below 550°C, a regrown layer of GaAs also doped with Ge is formed at the metallization/GaAs interface. The contact resistivity of 2-3×10 -7 Ω cm2 for this contact structure is nearly independent of the contact area from 900 to 0.2 μm2. Low-temperature Ohmic characteristics and thermal stability are also examined.