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, φB, was found to be as high as 0.96 eV with Pd metal. This indicated an 0.4 to 0.5 eV increase in φB compared with the room temperature (RT=300 K) deposition. For the diode fabricated at room temperature, the reverse saturation current density, J0, decreased sharply with the decrease of measuring temperature. The φB 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.