Amorphization mechanisms in Al{sub x}Ga{sub 1{minus}x}As

Bulk ion implantations of Al{sub x}Ga{sub 1{minus}x}As (x = 0.6 or 0.85) were performed at 77 K with 1.5 MeV Kr{sup +}, 1 MeV Ar{sup +} or 1.5 MeV{sup ++} ions, and the resulting damage state examined by using Rutherford backscattering spectrometry-channeling at 77 K and 293 K and transmission electron microscopy at 300 K. Amorphization of a portion of the Al{sub x}Ga{sub 1{minus}x}As layer occurred at 77 K only for the 1.5 MeV Kr{sup +} implantation, although the dose required to cause amorphization was higher for the higher Al content alloy. TRIM calculations show that with this implantation the density of high energy density cascades varies as a function of depth through the layer and that these are superimposed on a high, uniform density of defects. Comparison of the ion channeling spectra at 77 K and 293 K shows that recovery occurs over a portion of the layer in the Al{sub 0.6}Ga{sub 0.4}As but is not detected in the Al{sub 0.85}Ga{sub 0.15}As layer. In both alloys, the room temperature microstructure consists of an amorphous and a crystalline region. The amorphous region extends from the deeper Al{sub x}Ga{sub 1{minus}x}As/GaAs interface into the layer, and is separated from the crystalline materialmore » by a crystalline region containing planar defects. The difference between the alloys is in the extent of this latter region, which decreases in width with increasing Al content. These results will be used to examine current models for amorphization in the Al{sub x}Ga{sub 1{minus}x}As system.« less