Anomalous diffusion of acceptors in InP

Abstract

Diffusion or implantation of acceptors into InP substrates are important techniques for forming device junctions. Some recent studies of Be, Zn, Mg, Mn implants revealed anomalous post-annealed profiles with relatively flat tails and abrupt leading edges, especially in Fe-doped semi-insulating substrates. Such deep tails are detrimental for obtaining shallow p-n junctions. The experiments to be described were carried out using SIMS on two sets of InP samples: Be-implanted, Mn- or Zn-doped substrates; Zn-implanted n-ty InP substrates whose electron concentrations ( n ) varied from 5 × 10 15 to 2 × 10 18 e cm −3 . After anneal, the study of the correlations between the movement of the dopants in the substrates and the Be, Cr, Zn implants show that the flat tails and the abrupt leading edges depend strongly on: i) the presence and the concentrations of impurities, or dopants, located on indium sites; ii) the solubility of the p-type in-diffusing element; iii) the occupancy of the phosphorus sites by other substitutional elements, as sulphur for example.