Analysis of Electric Field and Thickness of Undoped-GaSb Single-Layer Samples using Photoreflectance Measurement

The purpose of this study is twofold: (1) to grow undoped-GaSb epitaxial structure on a high concentration n-GaSb substrate by molecular beam epitaxy and (2) to analyze the grown undoped-GaSb epitaxial structure through photoreflectance (PR) measurements. PR spectrum analysis of the undopedGaSb epitaxial layer at room temperature shows three notable features. First, in the region above the fundamental band gap Eg, the Franz-Keldysh oscillation (FKO) makes the PR signals oscillate. Second, low electric field PR is observed near Eg. Third, low energetic interference oscillations (LEIOs) occur in the region below the bandgap. An electric field is formed on the surface of the undoped-GaSb layer (i.e., in the interface between the undoped-GaSb and air); by using the FKO component, the calculated magnitude is 70 kV/cm at a growth temperature of 485 °C. In addition, the analysis of the FKO and low electric field PR data indicate a fundamental band gap Eg of 0.723 eV. The thickness of the undopedGaSb epi-layer, calculated using the LEIO PR spectrum, is 1040 nm.