Current transport in Pd/n-InP diodes formed at room and low temperature

Schottky contacts to n-InP have been made by deposition on substrates cooled to low temperature (LT=77 K) with a vacuum close to 10^-7 Torr. The Schottky barrier height, φ_B, was found to be as high as 0.96 eV with Pd metal. This indicated an 0.4 to 0.5 eV increase in φ_B compared with the room temperature (RT=300 K) deposition. For the diode fabricated at room temperature, the reverse saturation current density, J ₀, decreased sharply with the decrease of measuring temperature. The φ_B was increased from 0.48 to 0.71 eV, with the testing temperature decreased from 300 to 100 K, with a temperature coefficient of -6.1×10^-4 eV/K. The conduction mechanism was controlled by thermionic emission. For the LT diode, the value of J₀ was about six orders smaller than for the RT diode at the same temperature. As testing temperature decreased, the barrier height was increased from 0.96 to 1.15 eV, with a temperature coefficient of -3.2×10^-4 eV/K. The forward current had a saturation trend at a larger forward bias. In this region, the current was almost temperature independent and the transport mechanism was controlled by thermionic field emission.