In this letter, we report on heterostructure bipolar transistors (HBTs) bas
ed on silicon carbide (SiC) and a silicon carbide:germanium (SiC:Ge) alloy.
The SiC:Ge base alloy was formed by the ion implantation of Ge into p-type
4H-SiC and subsequent annealing. HBT mesa structures were fabricated using
a reactive ion etching process. The incorporation of Ge was found to incre
ase the gain and the Early voltage of the devices. A common-emitter current
gain (beta) of greater than 3 was measured for the SiC:Ge HBTs. Homojuncti
on SiC transistors were fabricated as a reference using the same process (e
xcept no Ge in the base region) and exhibited a beta of 2.2. The transistor
s exhibited high breakdown voltages (> 50 V without passivation), that typi
fy SiC-based devices. These results indicate that SiC:Ge is a promising mat
erial for use in SiC-based heterostructure devices. (C) 2001 American Insti
tute of Physics.