Electrical measurements and optical activation studies in Mg-implanted GaAs

Abstract

Mg ions were implanted in Cr‐doped semi‐insulating GaAs at 120 keV to doses of 3×10¹² to 1×10¹⁵/cm² at room temperature. Surface‐carrier concentrations and mobilities have been measured at various postimplantation anneal temperatures using the van der Pauw Hall‐effect/sheet‐resistivity technique. Detailed profiles of depth as a function of ion dose and anneal temperature are presented. Also, the results of a study of the integrated intensity of Mg emission at various annealing temperatures and of depth profiles of the relative emission intensity of the ions obtained by the photoluminescence method are compared with results obtained from electrical measurements. In addition, compensation‐level analysis and a comparison of theoretical diffusion profiles with depth‐profile data have been made. p‐type layers have been produced for all except the lowest dose of 3×10¹²/cm² after capping only (no postimplantation annealing) with pyrolytic Si₃N₄ encapsulants. Subsequent annealing up to 600 °C does not alter the electrical behavior appreciably. The electrical‐activation efficiencies obtained were as high as 85% for the sample having a dose of 1×10¹³/cm² annealed at 800 °C and 51% for the sample having a dose of 3×10¹⁴/cm² after capping only. In general, the depth profiles are very sensitive to annealing temperature and ion dose, broadening dramatically at or above the 700 °C annealing temperature, and producing an active layer which extends to roughly twice the projected range of the original implant.