Study of the internal electric fields across the interfaces in the GaAs/(1Al,Ga)As microstructures

The electro-optical properties of MBE grown selectively doped GaAs/Al _0.3 Ga _0.7 As heterostructures have been studied by photoreflectance spectroscopy. The spectra contained three types of oscillations in different spectra regions. The origins of different features in the spectra were identified by comparing the spectra after different layers were etched off, and under external electric fields. There are two types of spectra oscillations above the energy gap of the GaAs. The one with a large oscillation period was due to the modulation of the internal electric field in the cap region and the one with a small period originated from the space-charge region near the back GaAs/Al _0.3 Ga _0.7 As interface. The lineshape oscillations above the energy gap of Al _0.3 Ga _0.7 As originate from the undoped Al _0.3 Ga _0.7 As spacer. The internal electric fields were deduced from the spectra, and compared with the numerically calculated results.