Low-Temperature Synthesis of Polycrystalline Semiconductor Thin Films on Amorphous Substrates

Stanford researchers have patented a crystalline germanium nanostructure device and method of forming a continuous polycrystalline Ge film (5-500nm thick poly-Ge) with crystalline Ge islands of preferred orientation. A diffusion control layer between the metal and semiconductor layers allows controlled nucleation of (111)- oriented Ge crystallites on the Al seed layer. The method is suitable for Group IV and other semiconductors using a variety of metals, and their silicide and germinide compounds. The low cost, low temperature process has important applications in thin-film photovoltaic and electronics applications, such as thin-film transistors, solar cells, and flexible and large area electronics.

Stage of Research
Researchers have grown polycrystalline germanium (poly-Ge) thin films on both glass and polymer substrates at temperatures as low as 200 C. Germanium thin films with micron-size grains and (111) preferred orientation were prepared by controlled Ge nucleation and Ge lateral overgrowth of Al during a-Ge crystallization.