ELECTROMODULATION SPECTROSCOPY STUDY OF SYMMETRY FORBIDDEN TRANSITIONS IN AN INXGA1-XAS GAAS SINGLE-QUANTUM-WELL GROWN USING A TERTIARYBUTYLARSINE SOURCE/

The contactless electroreflectance (CER) and photoreflectance (PR) spe ctra of a single quantum well InGaAs/GaAs system have been measured at various temperatures between 20 and 300K. Unintentionally doped layer s were grown by low pressure metalorganic chemical vapor deposition us ing tertiarybutylarsine (TEA) as a substitute for AsH3. The Franz-Keld ysh oscillation (FKO) period can be related with the built-in electric field strength near the GaAs/InGaAs interface region. Symmetry forbid den transitions such as 1C-2H have often been observed. By varying the temperature of the sample, the built-in electric field can be changed by photo-induced voltages. The measurement results indicate that the main influence of temperature on the quantized transitions is dependen t on the band gap of the constituent material in the well. The measure d ratio of the amplitude of 1C-2H to 1C-1H transitions decreases with temperature. Its temperature dependence is similar to that of the buil t-in field. Therefore the existence of the built-in electric field may account for the observation of the symmetry forbidden transition 1C-2 H in the experiments.