Investigation of modulation-doped GaAs/AlGaAs single quantum well by photoreflectance

The interband transitions, built-in electric field, and energy of the two-dimensional electron gas (2DEG) of the modulation-doped GaAs/AlGaAs single quantum well at different temperatures (100–300 K) have been studied by the modulation spectroscopy of photoreflectance (PR). The built-in electric field was evaluated using the observed Franz–Keldysh oscillations and found to be increasing from 20±1 to 75±3 kV/cm with an increase in temperature from 100 to 300 K. In addition to the allowed quantum transitions, the forbidden transition 12L in the quantum well was also observed. Moreover, the energy level of the 2DEG was determined from the PR spectra and was found to decrease with the increasing temperature. The energy of the 2DEG of the higher doping sample is greater than that of the lower one.