Infrared study of hydrogen- and carbon-implanted heavily doped, <i>n</i>-type GaAs

Abstract

A study is given of the effect of ion implantation on the carrier density and the infrared dielectric constant of heavily doped, high-carrier density, n-type GaAs as measured by infrared reflection. Hydrogen ions were implanted at 300 keV at room temperature and carbon ions at 380 keV at near-liquid-nitrogen temperature. For H and C ions the effects of the implantation and subsequent annealing from 100 to 550 °C are examined. The 1H ion implantation and annealing results are compared with available SIMS data and with the carrier density profile obtained from capacitance-voltage measurements of a progressively etched sample. The 1H and carrier compensation profiles are clearly related and show a compensated layer ∼3 μm thick for the as-implanted samples. A deeply diffused layer is present after annealing and the depth grows with anneal temperature. After 500 °C annealing the carrier compensation in the diffused layer disappears but the original layer is still compensated. The 12C-implanted sample shows both carrier compensation and substantial damage-related changes in the dielectric constant. Annealing removes the damage-related changes and no compensated diffused layer such as that observed for hydrogen was present. An effective diffusion constant for the hydrogen related defect can be estimated but its value is dependent upon the model used. Different models give Deff=D0effe−Ea/kT with Ea about 1 eV but with D0eff values which are strongly model dependent.