Control of Schottky Barrier Height at Al/p-Ge Junctions by Ultrathin Layer Insertion

We have fabricated Al/p-Ge(100) junctions with an ultrathin GeO2 interfacial control layer and studied the effect of post-metallization annealing on the electrical properties from the current-voltage characteristics. Then, the changes in the chemical bonding features with annealing were directly evaluated by using hard x-ray photo-emission spectroscopy. Results of these analyses showed that a GeO2 reduction in the region near the Al/GeO2 interface occurs after annealing at temperatures over 300{degree sign}C and that the Fermi level pinning (FLP) effect increases. This suggests that inserting a thermally and chemically stable thin layer suppresses the FLP effect at the Metal/Ge interface caused by thermal annealing. The release of this FLP effect in Al/p-Ge junctions has also been demonstrated by using ultrathin N2 sputtered hafnium nitride layer instead of GeO2. And we found that the formation of a nitrogen rich region near the metal/Ge interface was an effective means of controlling the Schottky barrier height.