Effect of a skin-deep surface zone on formation of two-dimensional electron gas at a semiconductor surface

TL;DR

This study demonstrates that accurately modeling 2DEG band energies at semiconductor surfaces requires considering the physical surface's influence, beyond traditional electrostatic approaches, using angle-resolved photoelectron spectroscopy on sulfur-passivated InAs(001).

Contribution

It reveals the critical role of the physical surface in 2DEG band energy modeling, highlighting the necessity of boundary conditions beyond electrostatics.

Findings

Poisson-Schrödinger scheme predicts 2DEG band energies correctly when surface effects are included.

Surface properties significantly influence 2DEG wavefunctions and energies.

Experimental data confirms the importance of boundary conditions set by the physical surface.

Abstract

Two dimensional electron gases (2DEGs) at surfaces and interfaces of semiconductors are described straightforwardly with a 1D self-consistent Poisson-Schr\"{o}dinger scheme. However, their band energies have not been modeled correctly in this way. Using angle-resolved photoelectron spectroscopy we study the band structures of 2DEGs formed at sulfur-passivated surfaces of InAs(001) as a model system. Electronic properties of these surfaces are tuned by changing the S coverage, while keeping a high-quality interface, free of defects and with a constant doping density. In contrast to earlier studies we show that the Poisson-Schr\"{o}dinger scheme predicts the 2DEG bands energies correctly but it is indispensable to take into account the existence of the physical surface. The surface substantially influences the band energies beyond simple electrostatics, by setting nontrivial boundary conditions for 2DEG wavefunctions.