Diffusion and activation of n-type dopants in germanium

TL;DR

This study investigates the diffusion and activation behaviors of n-type dopants phosphorus and arsenic in germanium, revealing differences in electrical activation and the effects of implantation damage.

Contribution

It provides a comparative analysis of chemical and electrical dopant profiles in germanium and silicon, highlighting activation efficiencies and the impact of implantation damage.

Findings

P activation in Ge is similar to Si.

Arsenic shows poor activation in Ge.

Implantation damage does not significantly affect P activation.

Abstract

The diffusion and activation of $n$-type impurities (P and As) implanted into $p$-type Ge(100) substrates were examined under various dose and annealing conditions. The secondary ion mass spectrometry profiles of chemical concentrations indicated the existence of a sufficiently high number of impurities with increasing implanted doses. However, spreading resistance probe profiles of electrical concentrations showed electrical concentration saturation in spite of increasing doses and indicated poor activation of As relative to P in Ge. The relationships between the chemical and electrical concentrations of P in Ge and Si were calculated, taking into account the effect of incomplete ionization. The results indicated that the activation of P was almost the same in Ge and Si. The activation ratios obtained experimentally were similar to the calculated values, implying insufficient degeneration of Ge. The profiles of P in Ge substrates with and without damage generated by Ge ion implantation were compared, and it was clarified that the damage that may compensate the activated $n$-type dopants has no relationship with the activation of P in Ge.