Surface versus Impurity Doping Contributions in InAs Nanocrystals Field Effect Transistor Performance

TL;DR

This study distinguishes surface and impurity doping effects in InAs nanocrystal FETs, demonstrating how surface electrons and Cu impurities influence device performance, and introduces simulation methods for better doping control.

Contribution

It provides a comparative analysis of surface versus impurity doping in InAs nanocrystals and applies FET simulation techniques to understand their individual impacts.

Findings

Surface electrons contribute to n-type behavior in as-synthesized FETs.

Cu doping enhances n-type conduction via impurity incorporation.

Simulation methods effectively separate surface and impurity doping effects.

Abstract

The electrical functionality of an array of semiconductor nanocrystals depends critically on the free carriers that may arise from impurity or surface doping. Herein, we used InAs nanocrystals thin films as a model system to address the relative contributions of these doping mechanisms by comparative analysis of as-synthesized and Cu-doped nanocrystal based field-effect transistor (FET) characteristics. By applying FET simulation methods used in conventional semiconductor FETs, we elucidate surface and impurity-doping contributions to the overall performance of InAs NCs based FETs. As-synthesized InAs nanocrystal-based FETs show n-type characteristics assigned to the contribution of surface electrons accumulation layer that can be considered as an actual electron donating doping level with specific doping density and is energetically located just below the conduction band. The Cu-doped InAs NCs FETs show enhanced n-type conduction as expected from the Cu impurities location as an interstitial n-dopant in InAs nanocrystals. The simulated curves reveal the additional contribution from electrons within an impurity sub-band close to the conduction band onset of the InAs NCs. The work therefore demonstrates the utility of the bulk FET simulation methodology also to NC-based FETs. It provides guidelines for control of doping of nanocrystal arrays separately from surface contributions and impurity doping in colloidal semiconductor NCs towards their future utilization as building blocks in bottom-up prepared optoelectronic devices.