Hole trap level in Pt-Ti/p-InGaAs/n-InP heterostructures due to rapid thermal processing

Low-resistance ohmic contacts of Pt/Ti to p-InGaAs/n-InP heterostructures were formed by rapid thermal processing (RTP). Deep level transient spectroscopy and current-voltage temperature (I-V-T) measurements were used to characterize this system in order to evaluate the stability of the Pt/Ti ohmic contact and the effects of different RTP temperatures on the device performance. A new hole trap level with activation energy of 0.89 eV was found in samples treated at temperatures above 500 °C but not in those treated at lower temperatures. This trap, featured by a higher density when closer to the junction, was thought to be caused by Ti interdiffusion at high RTP temperature, in agreement with the analysis from Auger depth profiling. Four electron trap levels with activation energies of 0.61, 0.45, 0.35, and 0.30 eV were observed for all samples and believed to be native defects in InP. I-V-T measurements revealed current mechanisms independent of the RTP temperatures indicating that the new hole trap does not influence current conduction mechanisms.