RELIEF OF THERMAL-STRESS IN HETEROEPITAXIAL GAAS ON SI BY MESA RELEASE AND DEPOSITION

We demonstrate a mesa release and deposition (MRD) technology to realize stress relief in GaAs layers on Si, useful in practical device applications. A thin AlAs layer is incorporated in the heteroepitaxial GaAs layer about 1-mu-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 redeposition on the substrate after resist removal. We used spatially resolved photoluminescence on 100 X 200-mu-m2 GaAs-on-Si mesas before and after the MRD process to demonstrate the stress relief Uniform stress relief is found and the residual strain observed in the photoluminescence spectra at 77 K (0.05 +/- 0.02%) is attributed to strain thermally induced upon cooling from 300 to 77 K.