Growth kinetics and related physical/electrical properties of Ge quantum dots formed by thermal oxidationof Si1−xGex-on-insulator

Abstract

SiGe-on-insulator (SGOI) structures were thermally oxidized to form Ge quantum dots (QDs) that areembedded in a SiO2 matrix, to systematically investigate possible structural factors that affect the properties ofGe QDs, such as size, density and even position. The properties of Ge QDs depend stronglyon the layer thickness and the geometric pattern of SGOI structures, as well as on thethermal oxidation conditions and the Ge content of the SiGe alloy. Tiny dense(3 nm/2.8 × 1012 cm−2) Ge QDs are formedby oxidizing a Si0.95Ge0.05/Si-on-insulator ‘plane’ at 900 °C, which is highly promising for nanocrystal nonvolatile memory device applications. A single Ge QD(∼10 nm) forms and is self-aligned with electrodes viaSiO2 when a SGOI nanowire with a length of less than 150 nm is thermally oxidized. This meetsthe stringent criteria for a successful single-electron device. The growth kinetics of Ge QDsformed by the oxidation of SGOI planes and nanowires is discussed. Cathodoluminescencespectra were employed to investigate the origins of photoemission from the GeQDs/SiO2 system. Ge QD resonant tunnelling diodes are also fabricated to elucidate the transport ofelectrons through such a system.