Mesa release and deposition (MRD) method for stress relief in heteroepitaxially grown GaAs on Si

摘要

A mesa release and deposition (MRD) method realizes stress relief in GaAs layers on Si, useful in practical device applications. A thin AlAs layer is incorporated in the heteroepitaxial GaAs layer about l&mgr;m from the GaAs/Si interface. Mesas are etched down to the AlAs release layer and subsequently underetched in a 5% HF-solution at room temperature. Photoresist clamps keep the mesas in their exact position during the underetch process which results in a self-aligned re- deposition on the substrate after resist removal. Spatially resolved photoluminescence on GaAs on Si mesas before and after the MRD process was used to demonstrate the stress relief. GaAs epitaxy layers are thereafter grown on the GaAs on Si mesas. Spatially resolved photoluminescence was used to assess the strain level in the regrown layer. In contrast to the expected shift and splitting of the valence band of biaxially strained GaAs/Si, it was found that the peak shift of the band-to-band optical transition of the heteroepitaxial GaAs/MRD/Si to the GaAs reference at 77K is only 4nm and no valence band splitting was observed for the regrown layer.