High-performance p-channel polycrystalline-germanium thin-film transistors via excimer laser crystallization and counter doping

High-quality polycrystalline-germanium (poly-Ge) thin films have been successfully fabricated by excimer laser crystallization (ELC). Grains as large as 1 µm were achieved by ELC at 300 mJ/cm2. Meanwhile, the defect-generated hole concentrations in Ge thin films were significantly reduced. Furthermore, the majority carriers could then be converted to n-type by counter doping (CD) with a suitable dose. Then, high-performance p-channel Ge thin-film transistors (TFTs) with a high on/off current ratio of up to 1.7 × 103 and a high field-effect mobility of up to 208 cm2 V−1 s−1 were demonstrated for a channel width and length both of 0.5 µm. It was revealed that ELC combined with CD is effective for attaining high-performance p-channel poly-Ge TFTs.