Cryogenic processing of thin metal films

Cryogenic processing has been proven to be efficient in increasing Schottky contact barrier height, and significantly reducing device reverse leakage current. Metal-semiconductor-metal (MSM) photodetectors are widely used in optoelectronic integrated circuit (OEIC) receivers because of their compatibility with the preamplifier for their planar integration scheme, the minimum number of processing steps, high performance, and low cost. InGaAs/InP is usually chosen for the long wavelength application. However, there is always a potential problem of high dark current in an InGaAs/InP MSM photodetector due to the lower barrier height for such a material. In a recent study on Ag/InGaAs/InP contacts fabricated by a low temperature (LT) processing the Schottky barrier height was found to be as high as 0.64 eV. This value is more than double that of the same contact obtained by room temperature (RT) processing. Therefore, it is believed that the LT processing could greatly enhance the performance of a MSM photodetector. In this work, the effect of LT processing on the properties of thin metal films was investigated. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and in-situ resistivity measurements were conducted.