Low temperature fabrication of high mobility poly-Ge TFTs on plastic

Fabrication of depletion-mode poly Ge TFTs with field-effect hole mobility of 120 cm/sup 2//V-s on flexible PET substrates is reported. The fabricated TFTs show an ON/OFF ratio of 4/spl times/l0/sup 4/. All of the fabrication steps have been done at temperatures as low as 130/spl deg/C. A recently established stress-assisted copper-induced crystallization technique has been exploited to crystallize the amorphous Ge (a-Ge) layer. Mechanical compressive stress has been applied to the Ge layer by bending the flexible substrate inward. Proper patterning of the a-Ge layer before thermo-mechanical post-treatment alleviates the density of cracks induced in the Ge layer as the main repercussion of the interfacial stress.