Development and characterisation of improved ruthenium dopant sources

To form semi-insulating films capable of acting as current blocking layers and avoid intermixing of dopants and the consequent degradation of device properties the use of ruthenium (Ru) in indium phosphide (InP) has been studied. The conventional precursor bis(dimethylpentadienyl) ruthenium (DMRU) has significant limitations for atmospheric pressure-metal organic vapour phase epitaxy (AP-MOVPE) and to overcome the issues of low volatility, incorporation efficiency and stability under a hydrogen ambient a range of alternative Ru precursors were investigated, namely substituted cyclopentadienyl compounds of the general formula (RCP)(2)Ru. In this work we report the physical properties of a more complete series of samples to establish the most suitable chemicals for deposition trials. The most promising precursors were identified as bis(isopropylcyclopentadienyl)ruthenium ((iPrCP)(2)Ru) and bis(isobutylcyclopentadienyl)ruthenium ((iBuCp)(2)Ru) due to their superior volatility and stability. These materials were also assessed as precursors for AP-MOVPE to establish their incorporation characteristics and usefulness for the target devices compared with the conventional DMRU source. The results demonstrate controlled RU doping can be achieved using advanced source materials to provide access to novel device structures with enhanced performance capabilities. (C) 2008 Elsevier B.V. All rights reserved.