Control of the band-gap shift in quantum-well intermixing using a germanium interlayer

A simple technique for controlling the shift in band gap in AlGaAs/GaAs and InGaAs/GaAs quantum-well (QW) structures is reported. It involves the evap oration of a thin Ge layer and then covering it with spin-on silica followe d by rapid thermal annealing. The quantum-well intermixing was suppressed i n the presence of this Ge layer between the sample surface and the spin-on silica. The interdiffusion rate was reduced by more than one order of magni tude compared to that without the Ge interlayer. The blueshift of the band gap can be controlled by varying the thickness of the Ge interlayer. A diff erential band-gap shift of more than 100 meV can be achieved with a 500 A G e interlayer for both the AlGaAs/GaAs and InGaAs/GaAs QW structures. The op tical quality of the material was not deteriorated by the Ge cover compared to the SiO2 cover as seen from the photoluminescence intensity and spectra l linewidth. Using an appropriate mask, this technique has the potential to tune the band gap in selected areas across a single wafer. (C) 2000 Americ an Institute of Physics. [S0003-6951(00)02812-6].