Origine de la réduction de la durée de vie des photoporteurs dans le InGaAsP implanté à basse température
A semiconductor material used in the manufacture of terahertz (THz) antennas, the InGaAsP quaternary (E_g = 0,79 eV), is Fe-ion implanted followed by Rapid Thermal Annealing (RTA) in order to improve its emission properties. The annealing is required to recrystallize the layer that was amorphized during implantation, resulting in a polycrystal filled with recrystallization defects. However, the Fe-implanted materials provide better performance than those simply damaged with Ga. In order to disentangle the effect of recrystallization defects and of Fe impurities, Deep-Level Transient Spectroscopy (DLTS) measurements, current DLTS (I-DLTS) measurements and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) were carried out on non-implanted and on recrystallized samples. The DLTS et I-DLTS measurements aim to characterize deep levels generated by these two post-growth fabrication processes, while identifying the role of Fe impurities on the formation of these deep levels. In addition, a study of the vicinity of Fe atoms in the recrystallized material was performed using ToF-SIMS measurements. The DLTS measurements on recrystallized material were inconclusive because the capacitance measurements were distorted by the high resistivity of the material. On the other hand, the I-DLTS measurements on recrystallized material allowed us to conclude that the Fe impurities are responsible for the formation of a wide variety of energy levels lying between 0.25 and 0.40 eV, while structural defects induce levels lower than 0.25 eV. The Fe concentration is high compared to the solubility threshold of Fe in the material. It is therefore possible that Fe clusters are formed. However, this hypothesis is invalidated by the absence of a peak at the mass channels corresponding to the molecule ^(56)Fe_2^+ on ToF-SIMS mass spectra. Moreover, a simple model is used to estimate whether certain masses present on ToF-SIMS spectra correspond to actual bonds in the recrystallized material, not induced by the measurement. While no bonds with Ga and As were detectable, this model does not exclude the possibility of preferential binding between with In.
DLTS ToF-SIMS ion implantation THz antennas