Optimization of interface control layer for InP Schottky barriers

As compared with GaAs, the Schottky barriers on InP are generally not well behaved with low n-type Schottky barrier heights (SBH) and lack of reproducibility. Various approaches including use of special interfacial oxides have been tried to enhance SBH. However, many of such diodes suffer poor current transport characteristics, showing large leakage currents and low breakdown voltages. The values of the Richardson constant A** seems also to require attention according to a recent report. Therefore, not only SBH, but also the overall current transport including forward currents and reverse leakage currents should be optimized. The purpose of this paper is to attempt to control the SBH of the InP Schottky barrier by inserting a suitable interface control layer (ICL). For this purpose, various oxide ICLs formed by chemical etching, photochemical oxidation and laser-induced oxidation, and a semiconductor ICL utilizing an MBE grown ultrathin Si layer, were investigated. It is shown that the oxide ICL can enhance SBH to 0.7 eV for n-InP but with poor controllability of SBH. It was also found that the Richardson constant A** is anomalously small and that the reverse leakage current is large. On the other hand, Si ICL was found to be capable of controlling SBH in the range of 0-0.55 eV systematically by suitable doping into ICL, maintaining nearly ideal thermionic current transport