Excitonic electroabsorption in extremely shallow quantum wells

We report the remarkable observation of strong room-temperature excitonic features in the absorption spectra of GaAs-AlxGa1−xAs quantum wells (QWs) for values of x as low as 0.02. This has important implications for high-power modulators, since saturation intensities have been shown to be higher in QW modulators with low barriers. In addition, very shallow QWs have enhanced electroabsorption at small biases because of ease of ionization. In our p-i(multi-QW)-n device with x=0.02, we obtain a transmission change from 29% to 47% for a voltage change from +1 to −3 V.