Measurement of junction electric field in an MBE-grown modulation-doped GaAs/AlGaAs heterostructure by photoreflectance spectroscopy

Abstract

GaAs/AlGaAs modulation-doped heterostructures have recently been increasingly used in integrated circuits for the wireless communication industry, mainly for their high-speed capabilities. These high-quality heterostructures have been realized by molecular beam epitaxy (MBE). The Condensed Matter Physics Laboratory has recently been successful in growing GaAs/AlGAs modulation-doped heterostructures via MBE. In characterizing these samples, the photoreflectance (PR) technique has been used extensively in recent years to study modulation-doped structures. The PR spectrum includes the Franz-Keldysh Oscillations (FKOs) in the neighborhood of the GaAs and the AlGaAs band edge energies. From the analysis of these FKOs it is possible to measure the built-in electric field in the GaAs (acceptor) and AlGaAs (donor) regions. The authors have previously used the analysis of FKOs to calculate the surface electric field in a bulk GaAs layer using PR spectroscopy. In this paper, we demonstrate the investigation of our MBE-grown modulation-doped heterojunction; exploiting PR's sensitivity, ease-of-use and reliability even at room temperature measurements.