Impact of Sulfur Passivation on Carrier Transport Properties of In0.7Ga0.3As Quantum-Well MOSFETs

In-Geun Lee,Jun-Gyu Kim,Tae-Woo Kim,Dae-Hyun Kim,Hyeon-Bhin Jo

doi:10.1109/jeds.2021.3056689

Abstract

We investigated the impact of a sulfur passivation (S-passivation) process step on carrier transport properties of surface-channel In 0.7 Ga 0.3 As quantum-well (QW) Metal-Oxide-Semiconductor Field-Effect-Transistors (MOSFETs) with source/drain (S/D) regrowth contacts. To do so, we fabricated long-channel In 0.7 Ga 0.3 As QW MOSFETs with and without (NH 4 ) 2 S treatment prior to a deposition of Al 2 O 3 /HfO 2 = 1-nm/3-nm by atomic-layer-deposition (ALD). The devices with S-passivation exhibited a lower value of subthreshold-swing (S) = 74 mV/decade and more positive shift in the threshold voltage (VT) than those without S-passivation. From the perspective of carrier transport, S-passivated devices displayed excellent effective mobility (μ eff ) in excess of 6,300 cm 2 /V·s at 300 K. It turned out that the improvement of μ eff was attributed to reduced Coulombic and surface-roughness scatterings. Using a conductance method, a fairly small value of interface trap density (D it ) = 1.56 × 10 12 cm -2 eV -1 was obtained for the devices with S-passivation, which was effective in mitigating the Coulombic scattering at the interface between the high-k dielectric layer and the In 0.7 Ga 0.3 As surface-channel layer.

Highlights

Metal-oxide semiconductor field-effect transistors (MOSFETs) with an indium-rich InxGa1−xAs (x > 0.53) quantum-well (QW) channel have been extensively explored as an n-channel device for next-generation logic applications with an operating voltage (VDD) of 0.5 V or below, yielding excellent progress and accomplishments
For the past two decades, significant breakthroughs have been made on a variety of III-V MOSFETs by using atomic-layer-deposition (ALD), coupled with various surface pre-treatment and/or passivation process steps including sulfur passivation (S-passivation)
The device with S-passivation yielded a value of d2(ID)/d2(VGS) = 0.072 μA·μm−1 ·V−2, whereas the device without S-passivation 0.024 μA · μm−1 · V−2, indicating that there would be an improvement of the effective mobility in the device with S-passivation

Summary

INTRODUCTION

Metal-oxide semiconductor field-effect transistors (MOSFETs) with an indium-rich InxGa1−xAs (x > 0.53) quantum-well (QW) channel have been extensively explored as an n-channel device for next-generation logic applications with an operating voltage (VDD) of 0.5 V or below, yielding excellent progress and accomplishments. This is a consequence of their superior carrier transport properties, such as high electron mobility (μn_eff ) and virtual-source injection velocity (vinj) [1]. The devices with S-passivation exhibited outstanding electrical characteristics, including subthreshold-swing (S), effective mobility (μeff ) and interfacial properties. We found that the S-passivation helped to mitigate both Coulombic scattering due to the interface-state density (Dit) and surface-roughness scattering

FABRICATION PROCESS

RESULTS AND DISCUSSION

CONCLUSION