Blue shifts from doubly δ-doped heterostructures

A “Holy Grail” of optical communications and computing is the all-optical modulation of light; we present the results of a study of doubly doped quantum wells, which show that large blue shifts in the emission energies can be obtained with moderate laser pump powers using AlxGa1 − xAsInyGa1 − yAs heterostructures. The wide (about 50 nm) quantum wells are doped at the centre with Si and Be δ layers, separated by either 5 or 10 nm. The well and the band edge modulation within the wells therefore resemble those of bulk n-i-p-i structures. The photoluminescence spectra are dominated by broad band-to-band emission peaks, which exhibit a pronounced dependence on excitation power density. For a change in incident power of two orders of magnitude, the peak of the emission can shift by over 200 meV. Modelling of the confined states in these structures allows the emission to be assigned to spatially direct or indirect transitions.