ROOM-TEMPERATURE PHOTOLUMINESCENCE FROM MODULATION-DOPED ALGAAS/INGAAS/GAAS QUANTUM-WELLS

The photoluminescence (PL) spectral shape and position from single, modulation doped, and undoped AlGaAs/InGaAs/GaAs quantum wells have been studied at room temperature (RT) with the purpose of evaluating the usefulness of the PL technique for verifying device material structures. Starting with a general expression for the line shape, we can qualitatively predict the spectral shape and position by evaluation of the squared overlap integrals of the four possible transitions between the two lowest states in the valence and conduction band wells. A self-consistent calculation is used to determine the equilibrium wave functions and the energies of the bound states in the quantum well. Good agreement is found between the experimental and theoretical peak positions, and the Stark shift in the low-energy spectral onset between doped and undoped structures also can be closely reproduced. The accuracy of the calculations has been verified by comparing structures with varying layer widths and constant In composition, and vice versa. We demonstrate that the doping-induced electric field in the quantum well strongly affects the spectral shape of the PL signal. In fact, the dominant transition is typically from the first excited conduction band state to the valence band ground state. A sensitivity analysis restricted to the square of the overlap integrals and the peak wavelengths shows that changes in the quantum well parameters induced by changing the Ga and In fluxes can be separated for InGaAs mole fractions typically used in devices. This has also been verified by experiment.