Practical thermoreflectance design for optical characterization of layer semiconductors

Modulation spectroscopy is a powerful characterization tool of semiconductors. In this article, we present a practical design for implementing the thermoreflectance (TR) measurements of sheet-type materials more effectively. Detailed design diagrams of the electronic circuits and heater structure of the TR measurements are described. Duty-cycle and frequency responses of the heated pulses used in the TR measurements of layered GaSe are tested. The heated pulses of low frequency and long duty cycle seem to be more efficient in the periodic thermal perturbation of the layered crystals. The thermoreflectance of layer-type GaSe0.9S0.1 and GaSe0.8S0.2 as well as the polarized thermoreflectance (PTR) of layered ReS2 and ReSe2 are, respectively, carried out. The experimental spectra are detailed analyzed and discussed. Experimental analyses show the well-behaved performance of this thermoreflectance design. (C) 2004 American Institute of Physics.