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

摘要

We have fabricated Al/p-Ge(100) junctions with an ultrathin GeO_2 interfacial control layer and studied the effect of post-metallization annealing in N_2 ambience on the electrical properties from the current-voltage (I-V) characteristics. Then, the changes in the chemical bonding features with annealing were directly evaluated by using hard x-ray photo-emission spectroscopy (HAXPES). Results of these analyses showed that a GeO_2 reduction in the region near the Al/GeO_2 interface occurs after annealing at temperatures over 300 °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(100) junctions has also been demonstrated by using ultrathin N_2 sputtered hafnium nitride (HfN_x) layer instead of thermally-grown GeO_2. 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.