Deep level transient spectroscopy study of defects in hydrogen implanted p-type 4H-SiC

Abstract

p -type 4H-SiC epitaxial layers grown by chemical vapor deposition have been implanted with 200 and 100keV protons at five different implantation temperatures. An isochronal annealing series was performed from 100to1800°C, and Al-doped epitaxial layers have been characterized by means of deep level transient spectroscopy (DLTS) after each annealing step. DLTS measurements were carried out in the 150–670K temperature range and revealed the presence of eight hole traps located in the 0.18–1.8eV range above the valence band (EV). Heat treatments for temperatures above 700°C showed the progressive reactivation of the Al doping in the implanted region, which is completed after a 1500°C annealing treatment. Two traps located at EV+0.44eV and EV+1.8eV are persistent even after annealing at 1800°C, while the other traps anneal out after heat treatments at ⩽1700°C. An activation energy for dissociation of 6.2eV is estimated for the hole trap at EV+0.79eV, and the nature of this defect is discussed on the basis of previous experimental results and theoretical calculations. Furthermore, the study of the annealing behavior as a function of the implantation temperature shows that the detected traps display an increase of concentration for increasing implantation temperatures.