Photoluminescence of
Semiconductors OSD-104
Characterization of structure,composition, and impurities
Introduction
Photoluminescence spectroscopy (PL) is a powerful
optical method used for characterizing materials. PL
can be used to find impurities and defects in silicon andgroup III-V element semiconductors, and to determine
semiconductor band-gaps. A material absorbs light,
creating an electron-hole pair; an electron from thevalence band jumps to the conduction band leaving
a hole . The photon emitted upon recombination
corresponds to the energy-difference between thevalence and conduction bands, and is hence lower inenergy than the excitation photon.
Experimental setup
In order to measure photoluminescence ofsemiconductors, there are various requirements: (a) astable, powerful monochromatic light source, (b) optics tofocus light on the sample, (c) sample holder, (d) collection
optics, (e) monochromator, and (f) detector for spectral
analysis. Actual sample excitation and collection optics
used depend on the type of samples and experimental
conditions required. For some samples, excitation andcollection are optimal at 90°. In some cases it is also
important to map an entire semiconductor wafer toanalyze impurities found in different areas of the sample.
Computerized mapping can be done with a precision x-y
stage, and here usually the optics are positioned at zero
degrees to the sample.
Various experimental parameters derived from thespectra such as peak symmetry, FWHM of the peak,
center position of the peak, and fine structure, can giveinformation about the structure and composition of doped
semiconductors. This type of analysis can also be usedto evaluate growth methods using different input gasmixtures.

FeaturesBenefits

500 to 2000 nm operation

Unique system for continuous
monitoring from visible to IR without realignment

Integrated sample optics and vewer Optimize collected signal andaccurately target sample
Precision xy sample positioning

Automated mapping facility

Specifically designed for use withcryostatAmbient and low-temperaturecapabilities

Integrated data-collection andanalysis

Completely automated PL system

Figure 1 shows the optical and mechanical arrangementof the photoluminescence system for analysis andmapping of a semiconductor sample.
The sample is placed on the MapMax
x-y translational stage and fixed inFigure 2. Photoluminescence spectrum of doped GaAs.

The excitation light is chopped,
so that a lock-in amplifier can be used with an InGaAs
detector for data-acquisition. After the initial systemalignment is fixed, the experiment itself is controlled bycomputer using SpectraMax for Windows® spectroscopy
software.
Results
An example of a typical doped semiconductor
photoluminescence spectrum obtained with a HORIBA
Scientific system is shown in Fig. 2. Here, a liquidnitrogen-cooled InGaAs detector was used, for optimal
sensitivity and low noise. The entire experiment is
controlled by SpectraMax for Windows® software, which
provides easy data-acquisition and analysis.

Conclusions
A complete, nearly turn-key system forphotoluminescence measurements from HORIBA
Scientific is shown to produce spectra with high signal-tonoise ratio, for diagnostic testing of semiconductors andother materials. A HORIBA Scientific photoluminescencesystem provides a comprehensive solution forcharacterization of semiconductor materials.

info.sci@horiba.com
USA: +1 732 494 8660
UK: +44 (0)20 8204 8142
China: +86 (0)21 6289 6060

www.horiba.com/scientific
France: +33 (0)1 69 74 72 00
Italy: +39 2 5760 3050
Brazil: +55 (0)11 5545 1500

Germany: +49 (0)89 4623 17-0
Japan:+81 (0)3 6206 4721
Other:+33 (0)1 69 74 72 00

This document is not contractually binding under any circumstances - Printed in USA - ©HORIBA Scientific 07/2014

position in the sample holder.
The HORIBA Scientific Macro
Illuminator allows light to befocused on the sample while
the image is displayed on themonitor. An Ar+ laser is usedas the excitation source. Lightfrom the laser is focused intoa fiber, which goes into theinput channel of the HORIBA
Scientific Macro Illuminator.
The photoluminescence fromthe sample is collected, goes
through the output channelof the HORIBA Scientific
Macro Illuminator, into a fiber,and finally into the TRIAX550
monochromator for analysis.