Heterostructure Field Effect Transistors Fabricated from Germanium- Alloyed Silicon Carbide

摘要

For high power, high voltage applications, SiC would be more versatile if suitable heterojunction partners were available. Using ion implantation, we formed alloys of SiC with a few atomic percent of Ge. The Ge was implanted at 300 KeV and a dose of 1.67 x 1O(exp 16)cm(exp -2) into p-type, 4H-SiC, wafers. The wafers were annealed at temperatures up to 1 7000C. Raman Spectroscopy confirmed that the 4H structure was reconstructed after annealing. X-ray diffraction (XRD) Rutherford Backscattering spectrometry (RB S) showed an increase in the lattice constant, implying that some of the Ge was substitutional, and that the amount of substitutional Ge increased with annealing. Electrical conductivity showed only small changes, suggesting that the Ge is not a dopant, and does not significantly change the mobility. SiC:Ge/ SiC heterojunction devices were formed using Ti/Au as an electrical contact. Current-voltage (I-V) and capacitance measurements confirmed a reduction of the built-in voltage compared to similar SiC devices without Ge. The heterojunction forward current was found to behave as exp(qV/nkT), where the ideality factor (n) was 2. These results indicate that the SiC:Ge/SiC is promising for device applications.