Modulation of the high mobility two-dimensional electrons in Si/SiGe using atomic-layer-deposited gate dielectric

TL;DR

This study demonstrates the effective modulation of high mobility two-dimensional electrons in Si/SiGe heterostructures using atomic-layer-deposited Al₂O₃ as a gate dielectric, achieving high carrier densities with minimal leakage.

Contribution

It introduces a novel approach of using ALD Al₂O₃ as a gate dielectric to control 2DES in Si/SiGe heterostructures with improved uniformity and lower leakage compared to traditional methods.

Findings

Carrier density tunable from 2.5×10¹¹ to 4.5×10¹¹ cm⁻²

Minimal gate leakage current during tuning

Superior vertical modulation characteristics with ALD dielectric

Abstract

Metal-oxide-semiconductor field-effect transistors (MOSFET's) using atomic-layer-deposited (ALD) Al$_2$O$_3$ as the gate dielectric are fabricated on the Si/Si$_{1-x}$Ge$_x$ heterostructures. The low-temperature carrier density of a two-dimensional electron system (2DES) in the strained Si quantum well can be controllably tuned from 2.5$\times10^{11}$cm$^{-2}$ to 4.5$\times10^{11}$cm$^{-2}$, virtually without any gate leakage current. Magnetotransport data show the homogeneous depletion of 2DES under gate biases. The characteristic of vertical modulation using ALD dielectric is shown to be better than that using Schottky barrier or the SiO$_2$ dielectric formed by plasma-enhanced chemical-vapor-deposition(PECVD).