Photoreflectance spectroscopy of AlGaAs/GaAs heterostructures with a two-dimensional electron gas system

Abstract

Articles you may be interested inTwo dimensional electron transport in modulation-doped In0.53Ga0.47As/AlAs0.56Sb0.44 ultrathin quantum wells Correlation of the physical properties and the interface morphology of AlGaAs/GaAs heterostructures J. Appl. Phys. 94, 2464 (2003); 10.1063/1.1588360 Molecular beam epitaxial growth of normal and inverted two-dimensional electron gases in AlGaN/GaN based heterostructures J.We report a study of AlGaAs/GaAs semiconductor heterostructures with a two-dimensional electron gas system grown under different conditions by molecular beam epitaxy in three different laboratories. We performed photoreflectance ͑PR͒ measurements of this set of samples and analyzed the Franz-Keldysh oscillations associated with the E 0 transition of GaAs. We found that the sample with the highest electron mobility, as observed in Hall measurements at 77 K exhibited the lowest electric field strength. In addition, the 12 K photoluminescence ͑PL͒ spectra of the samples revealed intense and narrow free exciton luminescence in the sample with the highest electron mobility, while samples with lower mobility values showed impurities related PL lines. It is suggested that the electron mobility is affected by unintentional C impurities, which act like dispersion centers in the 2-DEG and increase the internal electric fields in the GaAs region. On the other hand, the PR spectra close to the AlGaAs band-gap energy region presented broad PR signals, due to the Si-doping in the alloy. The sample with the highest quality presented the most intense AlGaAs PR signal. We believe that low AlGaAs PR signal intensities are caused by unintentional incorporation of impurities during the preparation of the samples, which degrade the optical properties of the alloy.

Analysis of the band offsets between ultrathin GaN(000) layers and sapphire (0001) by photoelectron spectroscopy

“…Moreover, close to the interface an additional band bending might appear. Knowledge of band offsets are of special importance for the fabrication of GaN MOSFETs and devices using 2DEGs based on AlGaN/GaN or InGaN/GaN heterojunctions providing high electron mobilities [2][3][4][5][6]. Barriers for electrons and holes of at least 1eV are e.g.…”