DLTS and current transport studies of metal/InGaAs Schottky contacts

Schottky barrier enhancement by low temperature (LT=77 K) deposition has successfully achieved. The barrier height φ_B of 0.64 eV was obtained at LT, comparing the same contact formed at room temperature (RT) with a φ_B of 0.30 eV. Current transport mechanisms were studied on Schottky contacts formed at LT and RT. Based on theoretic fitting of the current-voltage (I-V) plots at different temperatures, it was found that the recombination current in the depletion region may be responsible for the I-V characteristics deviation from the ideal thermionic emission (EM) model. The recombination current can be caused by a deep defect level in InGaAs. This effect became more significant on diodes with lower barrier height, under lower bias, and at low measurement temperature. The generation current, however, has only a small effect on the reverse biased current. A deep defect level located at 0.321 eV below the bottom of the conduction band in InGaAs, identified by the deep level transient spectroscopy (DLTS) measurement, can act as the recombination-generation center. The generation lifetime of this center may be much longer than its recombination lifetime, so that it may affect the forward bias I-V characteristics more severely