Pp. 38-49 (12)
Terence K.S. Wong
A modulated spectroscopy method called photoreflectance is described. The technique involves
using an incident beam and a coincident modulating beam usually from a diode laser. The former results in a
reflectance signal while the latter gives a modulated reflectance signal. By fitting the spectrum of the
normalized modulated reflectance with a third order derivative of the dielectric function, the critical point
energies can be determined with high accuracy. Two photoreflectance spectroscopy instruments with high
throughput are discussed. The use of these instruments is illustrated by examples from biaxially stressed
silicon on insulator substrates and thin film photovoltaic devices. A recent method to suppress spurious
modulated light from entering the photodetector is also briefly discussed.
Photoreflectance, Modulated spectroscopy, Critical point, Strained silicon, Photovoltaics.
Division of Microelectronics School of Electrical and Electronic Engineering Nanyang Technological University