Electrooptical Properties of InGaAs/GaAs Strained Single Quantum Wells

The electrooptical properties of (100) and (111)B InGaAs/GaAs strained single quantum wells have been studied by the photoreflectance spectroscopy at various temperatures and under different biases. There is a Si δ-doping sheet under the GaAs surface to screen the surface built-in electric field from the quantum well. The spectral features consist of the excitonic interband transitions in the quantum well, and the Franz-Keldysh oscillations from the band edge transitions of the GaAs barrier near the surface. The piezoelectric field tilts the (111)B single quantum well toward the δ-doping and causes subband filling by the electrons from the δ-doping centers. With a proper external bias to repel electrons from the tilted quantum well, the excitonic interband transition in the (111)B system is enhanced.