Surface effect that causes a peak in band-edge photocurrent spectra: a quantitative model

Abstract

Band edge photocurrent spectra are typically observed in either of two shapes: a peak or a step. In this study, we show that the photocurrent band edge response of a GaN layer forms a peak, while the same response in GaN nanowires takes the form of a step, both are red-shifted to the actual band edge energy. Although this apparent inconsistency is not limited to GaN, the physics of this phenomenon has been unclear. To understand the physics behind these observations, we propose a model explaining the apparent discrepancy as resulting from a structure-dependent surface-effect. To test the model, we experiment with a GaAs layer showing that we can deliberately switch between a step and a peak. We demonstrate that using this quantitative model one may obtain the exact band edge transition energy, regardless of the red-shift variance, as well as the density of the surface state charges that cause the red shift. The model thus adds quantitative features to photocurrent spectroscopy.

11 pages, 4 figures

References in corpus (2)

• Atomistic Origin of Urbach Tails in Amorphous Silicon
• The Franz-Keldysh effect revisited: Electroabsorption including interband coupling and excitonic effects

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• Local Electric Field Measurement in GaN Diodes by exciton Franz-Keldysh Photocurrent Spectroscopy
• Probing dynamic behavior of electric fields and band diagrams in complex semiconductor heterostructures