Ge nanocrystals in MOS-memory structures produced by molecular-beam epitaxy and rapid-thermal processing

Abstract

ABSTRACTA method of forming a sheet of Ge nanocrystals in a SiO2layer based on molecular beam epitaxy (MBE) and rapid thermal processing (RTP) is presented. The method takes advantage of the very high precision by which a very thin Ge layer can be deposited by MBE. With proper choice of process parameters the nanocrystal size can be varied between ∼3 and ∼8 nm and the area-density between ∼1×1011and ∼1×1012dots/cm2. The tunneling oxide thickness is determined by the thickness of a thermally grown SiO2layer, and is typically 4 nm. C-V measurements of MOS capacitors reveal hole and electron injection from the substrate into the nanocrystals. Memory windows of about 0.2 and 0.5 V for gate-voltage sweeps of 3 and 6 V, respectively, are achieved.