Dissolution of donor-vacancy clusters in heavily doped n-type germanium

TL;DR

This study demonstrates that millisecond-flash lamp annealing can dissolve vacancy-donor clusters in heavily doped germanium, significantly increasing carrier concentration and reducing phosphorus diffusion, thus advancing Ge's integration into semiconductor technology.

Contribution

It provides a novel method to dissolve vacancy-donor clusters in heavily doped Ge, improving electrical properties and integration potential.

Findings

P4V clusters can be dissolved by flash lamp annealing at 1050 K

Carrier concentration increases over threefold after treatment

Phosphorus diffusion is suppressed post-annealing

Abstract

The n-type doping of Ge is a self-limiting process due to the formation of vacancy-donor complexes (DnV with n <= 4) that deactivate the donors. This work unambiguously demonstrates that the dissolution of the dominating P4V clusters in heavily phosphorus-doped Ge epilayers can be achieved by millisecond-flash lamp annealing at about 1050 K. The P4V cluster dissolution increases the carrier concentration by more than three-fold together with a suppression of phosphorus diffusion. Electrochemical capacitance-voltage measurements in conjunction with secondary ion mass spectrometry, positron annihilation lifetime spectroscopy and theoretical calculations enabled us to address and understand a fundamental problem that has hindered so far the full integration of Ge with complementary-metal-oxide-semiconductor technology.