Photoreflectance spectroscopy with white light pump beam

Abstract

Using a dual chopping scheme where both the pump beam and the probe beam are chopped, we show that it is possible to perform photoreflectance spectroscopy with a broadband white light source as the pump beam instead of a laser source. We show that although the signal strength is reduced by a factor of 1/π in the dual chopping scheme, it nevertheless has several advantages. A white light pump beam provides a wide range of excitation energy values, enabling one to characterize semiconductors of different band gaps spread over a wide energy range with a single modulation source. In the case of semiconductor heterostructures, simultaneous as well as selective excitation of different interfaces can be achieved easily. This technique is not plagued by the problem of background due to luminescence often encountered in low-temperature photoreflectance measurements. In this article, we present the details of this technique and demonstrate its usefulness by applying it to selected semiconductor heterostructure samples.