Sb-doped crystallization of densified precursor for n-type polycrystalline Ge on an insulator with high carrier mobility

Abstract

Low-temperature synthesis of polycrystalline (poly-) Ge on insulators is a key technology to integrate Ge-CMOS into existing devices. However, Fermi level control in poly-Ge has been difficult because poly-Ge has remained naturally highly p-type due to its defect-induced acceptors. We investigated the formation of n-type poly-Ge (thickness: 100–500 nm) using the advanced solid-phase crystallization technique with Sb-doped densified precursors. Sb doping on the order of 1020 cm−3 facilitated lateral growth rather than nucleation in Ge, resulting in large grains exceeding 15 μm at a low growth temperature (375 °C). The subsequent heat treatment (500 °C) provided the highest electron mobility (200 cm2/V s) and the lowest electron density (5 × 1017 cm−3) among n-type poly-Ge directly grown on insulators. These findings will provide a means for the monolithic integration of high-performance Ge-CMOS into Si-LSIs and flat-panel displays.