High hole mobility (≥500 cm² V⁻¹ s⁻¹) polycrystalline Ge films on GeO₂-coated glass and plastic substrates

Abstract

The highest recorded hole mobility in semiconductor films on insulators has been updated significantly. We investigate the solid-phase crystallization of a densified amorphous Ge layer formed on GeO2-coated insulating substrates. The resulting polycrystalline Ge layer with a glass substrate consists of large grains (~10 μm) and exhibits a hole mobility as high as 620 cm2 V−1 s−1, despite a low process temperature (500 °C). Even for the Ge layer formed on a flexible polyimide substrate at 375 °C, the hole mobility reaches 500 cm2 V−1 s−1. These achievements will aid in realizing advanced electronics, simultaneously allowing for high performance, inexpensiveness, and flexibility.