Photoreflectance spectroscopy of GaAs/AlGaAs quantum well structures

Abstract

Quantum well heterostructures are the primary components of a majority of semiconductor opto-electronic devices based on the III-V material system. For instance, quantum well structures are incorporated in the active region of semiconductor diode lasers in order to tailor the emission wavelength to a desired value and at the same time lower the threshold current levels. The performance of these devices therefore are heavily dependent on a) the parameters that define the quantum well structure, such as alloy composition, well width, well width uniformity, and b) the film quality of the quantum well structures. Various spectroscopic tools were developed and utilized to determine these much-needed parameters. Within the context of the Philippine setting, where we are staring to embark on compound semiconductor growth and device research, it becomes all the more imperative that we be familiar with these spectroscopic techniques. In this paper we demonstrate the efficacy of photoreflectance (PR) spectroscopy as a means to determine the well widths of GaAs/AlGaAs multiple quantum well films. The PR spectrum obtained shows sharp oscillating features and is attributed to excitonic transitions originating from the quantum well.