Semiconductor bandgap Report. In this work, transmission spectroscopy was used under continuous light excitation to determine the optical band gap of semiconductors. The experiment was performed using indirect and direct semiconductors, Gallium Phosphate

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Division of Electronic Engineering and Physics

Spectroscopy Determination of Semiconductor Bandgaps

Jonathan Hynd

November 2011 3rd Year Physics MSci.

1.

Abstract

The measurement of the band gap of materials is important in the semiconductor, nanomaterial and solar industries. In this work, transmission spectroscopy was used under continuous light excitation to determine the optical band gap of semiconductors. The experiment was performed using indirect and direct semiconductors, Gallium Phosphate (GaP) and Gallium Arsenide (GaAs) within a grating monochromator. The non-radiative relaxation processes are discussed in terms of the generated signal. A mechanism to describe the signal increase/decrease under the continuous excitation is presented. The results obtained were 1.41eV and 2.33eV for GaAs and Gap respectively which are consistent with the accepted values of 1.43eV and 2.26eV showing that this method was useful to locate the band gap directly from the optical absorption spectra.

2. Introduction

Energy bands consisting of a large number of closely spaced energy levels exist in crystalline materials. The bands can be thought of as the collection of the individual energy levels of electrons surrounding each atom. The wavefunctions of the individual electrons, however, overlap with those