Lateral Transport and Field-Effect Characteristics of Sputtered P-Type Chalcogenide Thin Films

TL;DR

This study investigates lateral electrical transport in sputtered p-type chalcogenide thin films and multilayers, demonstrating improved mobility and transistor performance, with insights into process optimization for electronic device applications.

Contribution

It provides new measurements of mobility and transistor characteristics in sputtered p-type chalcogenides, and explores process optimizations for device performance enhancement.

Findings

Sb2Te3/GeTe superlattices have highest Hall mobility (~18 cm2/V/s).

Ultrathin Ge2Sb2Te5 transistors achieve mobility ~5.5 cm2/V/s and on/off ratio ~10000.

Process optimizations like AlOx capping affect device mobility and performance.

Abstract

Investigating lateral electrical transport in p-type thin film chalcogenides is important to evaluate their potential for field-effect transistors (FETs) and phase-change memory applications. For instance, p-type FETs with sputtered materials at low temperature (<= 250 C) could play a role in flexible electronics or back-end-of-line (BEOL) silicon-compatible processes. Here, we explore lateral transport in chalcogenide films (Sb2Te3, Ge2Sb2Te5, Ge4Sb6Te7) and multilayers, with Hall measurements (in <= 50 nm thin films) and with p-type transistors (in <= 5 nm ultrathin films). The highest Hall mobilities are measured for Sb2Te3/GeTe superlattices (~18 cm2/V/s at room temperature), over 2-3x higher than the other films. In ultrathin p-type FETs with Ge2Sb2Te5, we achieve field-effect mobility up to ~5.5 cm2/V/s with current on/off ratio ~10000, the highest for Ge2Sb2Te5 transistors to date. We also explore process optimizations (e.g., AlOx capping layer, type of developer for lithography) and uncover their trade-offs towards the realization of p-type transistors with acceptable mobility and on/off current ratio. Our study provides essential insights into the optimization of electronic devices based on p-type chalcogenides.