Contactless electroreflectance approach to study the Fermi level position in GaInNAs/GaAs quantum wells

Abstract

A fruitful approach to study the Fermi level position in GaInNAs/GaAs quantum wells (QWs) has been proposed in this paper. This approach utilizes contactless electroreflectance (CER) spectroscopy and a very simple design of semiconductor structures. The idea of this design is to insert a GaInNAs quantum well (QW) into a region of undoped GaAs layer grown on n-type GaAs substrate. The possible pinning of the Fermi level in the GaInNAs QW region modifies band bending in this system. In CER spectra both QW transitions and GaAs-related Franz-Keldysh oscillations (FKOs) are clearly observed. The analysis of QW transitions allows one to determine the band gap discontinuity at GaInNAs/GaAs interface whereas the analysis of FKOs allows one to determine the built-in electric field in the GaAs cap layer, and, finally, one is able to find the Fermi level pinning in GaInNAs QW region.

Contactless electroreflectance spectroscopy of optical transitions in low dimensional semiconductor structures

“…The application of CER spectroscopy to study low dimen− sional heterostructures allows to investigate various mate− rial issues like (i) the built−in electric field including the Fermi−level position [7][8][9][10]15], (ii) the band−offset at semi− conductor interfaces [11][12][13][14], (iii) the homogeneity of low dimensional systems [16], (iv) the carrier localization effect including the Stokes shift [17], as well as other issues/ effects [18]. Some examples of the application of CER spec− troscopy to study selected material systems/heterostructures are presented below.…”

“…These defects want to pin the Fermi−level at the Fermi stabilization energy [15,42]. It is possible to observe this effect in CER spectroscopy due to its high sensitivity to the built−in electric field which for bulk−like materials is manifested by FKO [7]. Figure 6 shows CER spectra measured at room tempera− ture for Ga 0.78 In 0.28 N x As 1−x /GaAs QW structures of various nitrogen concentrations.…”

“…The periodic modulation of a built−in electric field inside the sample pro− duces sharp spectral features at photon energies which cor− respond to inter−band transitions. Due to the Franz−Keldysh effect, CER spectroscopy can be also applied to investigate the built−in electric field and the Fermi−level position in semiconductor heterostructures [7][8][9][10]. For recent years CER spectroscopy was widely applied to study various material issues in different semiconductor materials and heterostructures .…”

Contactless and soft contact electroreflectance of AlGaN/GaN and GaN/AlGaN/GaN field effect transistor heterostructures

“…In addition, the application of CER spectroscopy to AlGaN/GaN system allows an investigation of the built-in electric field in AlGaN layer because of its sensitivity to the Franz-Keldysh effect [6,7]. So far CER spectroscopy has been successfully applied to study Franz-Keldysh oscillations (FKOs) in AlGaN/GaN FET structures [4,5,8,9] and also other III-V semiconductor structures [10,11]. In this work the AlGaN/GaN heterostructures with a thin GaN cap layer and without this cap layer were investigated by the CER and soft contact electroreflectance (SCER) spectroscopies.…”

Photoreflectance spectroscopy of the band bending and the energy gap for Mg‐doped InN layers

“…In this work we have applied phororeflectance (PR) to investigate the band bending and the energy gap for Mg-doped InN layers of various Mg concentrations. PR spectroscopy is known as a contactless, nondestructive and very powerful method to investigate the built-in electric field (band bending) and the energy gap in semiconductor structures [20][21][22]. Despite many advantages of PR spectroscopy this technique was not applied widely to investigate InN layers, especially Mg-doped InN layers.…”