The electrical characteristics of single‐crystalline grown on a Si substrate and the heterojunction system have been investigated to determine their suitability for the application to heterojunction bipolar transistors. Arsenic and phosphorus ion implantation and subsequent furnace annealing were found to provide n‐type layers with the sheet resistivity of several hundred ohm/square. The current‐voltage characteristics can be given as , where the value of n is around 1.35. Heterojunction bipolar transistors using as a wide‐gap emitter were realized for the first time and compared with previously reported Si‐based HBT's. The performance of our wide‐gap emitter becomes superior to others at large base Gummel numbers.