The properties of epitaxial pure germanium films on silicon substrate

To fabricate avalanche photodiodes with less multiplication noises based on germanium, the properties of epitaxial Ge films on silicon substrate are studied. Ge layers are grown directly on an Si substrate by using surfactant-mediated epitaxy (SME) in the molecular beam epitaxy (MBE) growth. Transmission electron microscopy (TEM) and double-crystal X-ray diffraction (XRD) are performed. From the results, we can obtained relaxed, pure and high quality Ge layers. The crystal quality of the sample with implanted p-n junction are better than that of the sample with epitaxial p-n junction. Hole mobility determined by Hall measurements reaches almost 300 cm²/Vs. Properties of sample with an implanted p-n junction are quite good. Reverse breakdown voltage is 50-100 V and forward-conducting voltage is 0.3-0.5 V