Si/Si/sub 1-x-y/Ge/sub x/C/sub y/Si heterojunction bipolar transistors

Recently great interest in silicon-based heterojunction devices has been caused by high-speed Si/sub 1-x/Ge/sub x/ base HBTs with f/sub t/ exceeding I00 GHz. To extend silicon heterojunction technology beyond strained Si/sub 1-x/Ge/sub x/,, several groups have pursued Si/sub 1-x-y/Ge/sub x/C/sub y/ alloys, which are ofinterest because carbon is expected to allow the possibility of strain-free silicon heterostructures which will eliminate a major constraint on device design. Several groups have succeeded in growing strain compensated Si/sub 1-x-y/Ge/sub x/C/sub y/ layers on silicon, but to date there have been no Si/sub 1-x-y/Ge/sub x/C/sub y/ electrical devices of any kind or experimental bandgap studies reported. In this paper we present the first electrical devices of any kind containing Si/sub 1-x-y/Ge/sub x/C/sub y/ alloys and present preliminary measurements of Si/sub 1-x-y/Ge/sub x/C/sub y/ bandgaps. Temperature studies of these HBT devices indicate that the partially strain compensated Si/sub 1-x-y/Ge/sub x/C/sub y/ bandgap remains comparable to the bandgap of strained Si/sub 1-x/Ge/sub x/, a most surprising and fortuitous result.<
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