A silicon-graphene-silicon transistor with an improved current gain

In history, semiconductor-metal-semiconductor transistor (SMST) was proposed for frequency improvement. However, a general fabrication method is still missing due to the unsolved technological problem of deposition of a general crystalline semiconductor on metal, and a thinner metal base is also difficult to be fabricated with high quality. Recently, due to the atomic thickness of graphene, the concept of semiconductor-graphene-semiconductor transistor (SGST) has emerged which leads to the renaissance of SMST, however the experimental study is in its infancy. In this letter, SMST and SGST are fabricated using Si membrane transfer. It is found the common base current gain can be improved from about 0.5% in a Si-Au-Si transistor to about 1% in a Si-Gr-Ge one, and to above 10% in a Si-Gr-Si one, which is attributed to both the ultra-thin thickness and the quantum capacitance effect of graphene.