Comparison between results of optical and electrical measurements of free electron concentration in n-InAs specimens

Tatyana G Yugova,Irina B Parfent'Eva,Aleksandr G Belov,Stanislav N Knyazev,Vladimir E Kanevskii,Evgeniya I Kladova

doi:10.3897/j.moem.7.3.76700

Abstract

A theoretical model has been developed for determining the free electron concentration in n-InAs specimens from characteristic points in far IR reflection spectra. We show that this determination requires plasmon-phonon coupling be taken into account, otherwise the measured electron concentration proves to be overestimated. A correlation between the electron concentration Nopt and the characteristic wavenumber ν+ has been calculated and proves to be well fit by a third order polynomial. The test specimens have been obtained by tin or sulfur doping of indium arsenide. The electron concentration in the specimens has been measured at room temperature using two methods: the optical method developed by the Authors (Nopt) and the conventional four-probe Hall method (the Van der Pau method, NHall). The reflecting surfaces of the specimens have been chemically polished or fine abrasive ground. The condition Nopt &gt; NHall has been shown to hold for all the test specimens. The difference between the optical and the Hall electron concentrations is greater for specimens having polished reflecting surfaces. The experimental data have been compared with earlier data for n-GaAs. A qualitative model explaining the experimental data has been suggested.

Highlights

The information value of experimental data increases greatly if the target parameter can be measured using different methods
For this reason data obtained with these methods may differ. It was shown [1] that the free electron concentrations in n-GaAs calculated on the basis of Hall effect (NHall) may be either lower or higher than those determined from far IR reflection spectra (Nopt)
A theoretical model was developed for determining the free electron concentration in n-InAs specimens (Nopt) from characteristic points in far IR reflection spectra

Summary

Introduction

The information value of experimental data increases greatly if the target parameter can be measured using different methods. It should be noted that free carrier concentration data obtained by electrical measurements represent the whole specimen bulk while those obtained by optical measurements only refer to the narrow superficial layer of the specimen. For this reason data obtained with these methods may differ. It was shown [1] that the free electron concentrations in n-GaAs calculated on the basis of Hall effect (NHall) may be either lower or higher than those determined from far IR reflection spectra (Nopt). By analogy with the cited work [1] in which tellurium-doped gallium arsenide specimens were studied we present below the optical and electrical measurement data for sulfur- and tin-doped n-InAs specimens

Experimental

Results and discussion

Conclusion