Implantation and annealing of Cu in InP for electrical isolation: microstructural characterisation

The formation of metallic precipitates to produce embedded Schottky barriers within a conductive layer has been investigated as a potentially new form of implantation-induced isolation. Accordingly, Cu-implanted InP has been characterised with Rutherford backscattering spectrometry, transmission electron microscopy and secondary ion mass spectrometry as functions of implantation and annealing temperatures. Substrates implanted at room temperature were amorphised, resulting in greater post-anneal disorder in the form of microtwins and dislocations. However, annealing-induced Cu diffusion was reduced in such samples as attributed to gettering at end-of-range disorder. Additional defect centres, potentially Cu-based precipitates, were also observed. Further to the structural characterisation presented herein, complementary electrical measurements are necessary to deduce the appropriate combination of residual disorder and precipitate concentration to yield electrical compensation. This will ultimately determine the viability of this isolation technology for producing extremely resistive substrates for very high frequency devices.