Determination of surface electric potential by photoreflectance spectroscopy of HEMT heterostructures

Photoreflectance and Raman Study of Surface Electric States on AlGaAs/GaAs Heterostructures

“…The w-FKO is observable with both lasers, which indicates that it originates from the surface GaAs layer. In previous reports this feature has been associated with the surface electric field [31]. Finally, at 1.8 eV we can see the feature originates from the AlGaAs layers, which offers information about energy band gap and consequently of the Al concentration.…”

“…Specifically, with AlGaAs/GaAs heterostructures there are reports about the effect of the surface on the electronic properties. In particular, the relationship between the surface electric field and electron mobility in the two-dimensional electron gas (2DEG) achieved in the AlGaAs/GaAs interface has been studied [21][22][23][24][25][26][27][28][29][30][31]. Other studies with heterojunction bipolar transistors [32], high electron mobility transistors [33][34][35], quantum Hall effect [36], and nanostructure-based devices [37][38][39][40][41] have been reported.…”

“…Photoreflectance and Raman spectroscopy are very useful approaches that have been widely used for the study of GaAs-based devices [4,[23][24][25][26][27][28][29][30][31]. The PR technique has been used to study the AlGaAs/GaAs system in numerous reports, which were focused on determining the origin of Franz-Keldysh oscillations (FKO) that usually are observed at the PR spectra [24][25][26][27][28][29][30][31]. Today we know that wide-period FKO observed between 1.42 and 1.7 eV are associated with the surface electric field and short-period FKO just above 1.42 eV originate from internal AlGaAs/GaAs interfaces [31].…”

“…The PR technique has been used to study the AlGaAs/GaAs system in numerous reports, which were focused on determining the origin of Franz-Keldysh oscillations (FKO) that usually are observed at the PR spectra [24][25][26][27][28][29][30][31]. Today we know that wide-period FKO observed between 1.42 and 1.7 eV are associated with the surface electric field and short-period FKO just above 1.42 eV originate from internal AlGaAs/GaAs interfaces [31]. In the Raman spectroscopy case, there are many reports where it is employed as a useful tool to explore the surface passivation of GaAs films and AlGaAs/GaAs heterostructures.…”