High resolution microscopy of Pd/InP interfaces

Depositing Pd on InP at cryogenic substrate temperatures has previously been found to significantly increase the barrier height of the resulting Schottky diode. In this work, bulk samples of Pd/n-InP were fabricated using substrate temperatures of 300K (RT) and 77K (LT). The structural differences between the RT and LT samples were then studied using Cross-Sectional Transmission Electron Microscopy (XTEM), Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD), Auger Electron Spectroscopy (AES), and Secondary Ion Mass Spectroscopy (SIMS). The XTEM and depth profiling results indicated that the RT samples had an amorphous interaction layer approximately 150angstrom thick, while the LT samples had an interfacial layer less than 30angstrom thick. Therefore, depositing Pd at low temperatures greatly reduced the interaction between Pd and InP. XRD lines corresponding to (111) and (200) Pd were obtained as well. The lines in the RT case had a greater integrated intensity than in the LT case, indicating that the RT Pd had a higher degree of crystallinity. AFM was used to compare the morphology of the LT and RT Pd surfaces as a function of metal thickness.