Epitaxial n++-InGaAs ultra-shallow junctions for highly scaled n-MOS devices

Abstract

[EN] High electron mobility III-V semiconductors like InGaAs are excellent candidates for sub-10 nm n-metal-oxide-semiconductor (nMOS) devices. One of the critical challenges in downscaling III-V devices is achieving low-resistance contacts by forming low-defect, ultra-shallow junctions <9 nm in depth, with n-type dopant concentrations above 10 cm . In the current study, we combine time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profile analysis, atomic force microscopy (AFM) imaging, and high-resolution transmission electron microscopy (HR-TEM) to determine the optimal doping strategy for growing Si-doped n-InGaAs ultra-shallow junctions by molecular beam epitaxy. We test three different approaches to doping: homogeneous co-deposition, single δ-layer (continuous) doping, and triple δ-layer (pulsed) doping. We demonstrate the formation of technologically suitable n-InGaAs junctions 5–7 nm deep, grown under As-rich conditions with a single δ-layer at temperatures as low as 400 °C. These junctions have peak Si concentrations between 6 × 10 and 1 × 10 cm and high crystal quality. The surface self-organizes into smooth ripples or mounds, up to a peak dopant concentration of ~2 × 10 cm Above this value, enhanced diffusion of Si and In due to a large population of Ga vacancies increases lattice strain in the semiconductor epilayer, triggering a transition from 2D growth to 3D growth and the formation of InGaAs clusters on the surface.