Effect of the Surface on Optical properties of AlGaAs/GaAs heterostructures with double 2-DEG
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Effect of the Surface on Optical properties of AlGaAs/GaAs heterostructures with double 2-DEG
L. Zamora-Peredo1*, I. Cortes-Mestizo1, L. García-Gonzalez1, J. Hernandez-Torres1, D. Vázquez-Cortes2, S. Shimomura2,A. Cisneros3, V. Méndez-García3 and M. Lopez-Lopez4. 1
Centro de Investigación en Micro y Nanotecnología, Universidad Veracruzana, Calzada Adolfo Ruiz Cortines # 455, Fracc. Costa Verde, C.P. 94292, Boca del Río, Veracruz, México. 2 Graduate School of Science and Engineering, Ehime University, 3 Bukyo-cho, Matsuyama, Ehime 790-8577, Japan. 3 Coordinación para la Innovación y Aplicación de la Ciencia y Tecnología, Universidad Autónoma de San Luis Potosí, Av. Karakorum No. 1470, Lomas 4a Secc., San Luis Potosí, S.L.P. 78210, México. 4 Departamento de Física, Centro de Investigaciones y de Estudios Avanzados - IPN, México D. F., México ABSTRACT In this work we studied a set of heterostructuresAlGaAs/GaAs by photoreflectance (PR) and photoluminescence (PL) spectroscopy in order to determine the effect of the surface on optical properties of a symmetric double two-dimensional electron gas(2DEG). The potential profiles of the edge of the conduction band were modeled by nextnano software. By Hall effect measurements at 77K we determined the electron mobility of the samples. Thesurface electric field was calculated by the analysis Franz-Keldysh oscillations observed in thePR spectra.Thecalculation of the band structure shows that the surface electric field prevents the creation of 2DEG closest to the surface. PL spectra shows a peak originated in thedeepest AlGaAs layer, close to the 2DEG region,associated with to the free exciton whose intensity increases as the electric field decrease. INTRODUCTION Usually, the electronic characteristics of the semiconductor devices can be affected by the properties of its surface. In order to eliminate chemical instability that may cause undesired effects it is well established that the surfaces of semiconductor-based devices have to be treated properly. Frequently, the surfaces of semiconductor devices are passivated in order to stabilize their chemical nature and to eliminate reactivity [1-4]. In the AlGaAs/GaAsheterostructures case, is possible to study the effect of the surface on the electronic properties of a 2DEG by electrical measurements [3, 4], inspecific the relationship between the surface electric field and the electron mobility. Optical approaches like photoreflectance and photoluminescence spectroscopy are very useful techniques that have been widely used for the study and characterization of AlGaAs/GaAs system [5-11]. Some reports have been focused to determinate the origin of FranzKeldyshoscillations (FKO) that usually are observed at the PR spectra, now we know that wideperiod FKO are associated to surface electric field and short-period FKO are originated by
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internal AlGaAs/GaAs interfaces [9-11]. In this work, we studied a set of heterostructures by PR and PL measurements in order to determinate the effects of the surface electric fieldover the condu
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