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Work function of GaAs(hkl) and its modification using PEI: mechanisms and substrate dependence
Samuel D Seddon1, Christopher Benjamin, James I Bryant
1Department of Physics, University of Warwick, Coventry, CV4 7AL, UK. gavin.bell@warwick.ac.uk.
Physical Chemistry Chemical Physics : PCCP
|November 2, 2019
Summary
Spin-coating poly(ethylenimine) (PEI) reduces the work function of gallium arsenide (GaAs) surfaces. This work function reduction is stable in air for over a year, with PEI influencing semiconductor doping and surface dipoles.
Area of Science:
- Materials Science
- Surface Science
- Semiconductor Physics
Background:
- Gallium arsenide (GaAs) is a crucial semiconductor material.
- Modifying semiconductor work functions is essential for device performance.
- Poly(ethylenimine) (PEI) is a polymer with potential surface modification applications.
Purpose of the Study:
- To investigate the effect of poly(ethylenimine) (PEI) spin-coating on the work function of various GaAs crystal faces.
- To analyze the stability of PEI coatings and their degradation mechanisms in ambient air.
- To understand the surface dipole formation and doping effects of PEI on GaAs.
Main Methods:
- Spin-coating of PEI onto different GaAs crystal faces (001, 110, 111A, 111B).
- Work function measurements using Kelvin probe force microscopy (KPFM).
- Core-level photoemission spectroscopy to study PEI degradation.
- Analysis of surface dipole and doping effects.
Main Results:
- PEI coating significantly reduces the GaAs work function (0.51–0.69 eV), dependent on crystal face, doping, and termination.
- Work function reduction persists (0.2–0.3 eV) after one year in air, despite initial decay.
- PEI degradation in air involves reactions with CO2 and H2O.
- PEI induces surface doping and dipole formation, affecting band bending, especially in p-doped GaAs.
Conclusions:
- PEI is an effective material for reducing and stabilizing the work function of GaAs surfaces.
- The surface dipole and doping effects of PEI must be considered for semiconductor device applications.
- PEI coatings offer long-term stability, making them promising for modifying GaAs interfaces.
