Light emission spectra of AlGaAs/GaAs multiquantum wells induced by scanning tunneling microscope

We have investigated the scanning-tunneling-microscope light emission (STM-LE) spectra of $\mathrm{p-}{\mathrm{Al}}_{\mathrm{0.4}}{\mathrm{Ga}}_{\mathrm{0.6}}\mathrm{As}\mathrm{/p-}\mathrm{GaAs}$ multiquantum wells. The injection current level was kept as low as 0.1–0.5 nA to ensure that the sample is not damaged by the tunneling current. This is the current level ordinarily used for taking STM images. The peak energy of the emission shifts to the high energy side with decreasing well widths. A corresponding peak shift behavior was also observed in the photoluminescence (PL) spectra for the same samples. From comparisons of the STM-LE and the PL spectra, we find that although there is a difference in the excitation process, the final recombination process is identical in both cases.