Strain in GaAs by low-dose ion implantation

Abstract

The production of strain in (100) GaAs by low-dose ion implantation has been investigated. Implantations were conducted at room temperature with ions of He, B, C, Ne, Si, P, and Te. Energies were between 100 and 500 keV, and each species was implanted over a range of doses sufficient to create perpendicular strain below 0.3%. The perpendicular strains ε ⊥ were measured by x-ray double-crystal diffractometry about the (400) Bragg condition. Detailed depth profiles of ε⊥ were obtained by fitting the resulting rocking curves with a kinematic model for the diffraction. For all implantations the maximum in the ε⊥ distribution was found approximately from the separation of the lowest-angle prominent oscillation from the substrate peak. The depth profiles of perpendicular strain had the same shape as the calculated profiles of energy deposited per ion by nuclear collisions, FD. The maximum perpendicular strains scaled linearly with the dose φ of the implanted ions for all ion species. Also the ratio of maximum strain to dose was found to vary linearly with FD over more than 2 orders of magnitude in FD. We therefore conclude that ε⊥=KφFD at all depths, where K is a constant. The value of K was found to be (5±1)×10−2 Å3/eV. Our results suggest that this holds for any ion species in the mass range 4–128 amu, with energy in the hundreds of keV, implanted into (100) GaAs at room temperature, provided the maximum strain is less than 0.3%.