Ti-doped Gallium Phosphide Layers with Concentrations Above the Mott Limit
- PDF / 143,601 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 75 Downloads / 163 Views
1210-Q03-17
Ti-doped gallium phosphide layers with concentrations above the Mott limit Javier Olea1, David Pastor1, María Toledano-Luque1, Ignacio Mártil1, Germán González-Díaz1, Jordi Ibáñez2, Ramón Cuscó2 y Luis Artús2. 1 Dpto. De Física Aplicada III (Electricidad y Electrónica). Facultad de Ciencias Físicas. Universidad Complutense de Madrid. E-28040 Madrid. Spain. 2 Institut Jaume Almera, Consejo Superior de Investigaciones Científicas (CSIC), Lluís Solé i Sabarís s/n, 08028 Barcelona, Spain. ABSTRACT We have studied the Pulsed-Laser Melting (PLM) effects on Ti implanted GaP to form an Intermediate Band (IB). Structural analysis has been carried out by means of Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), Raman spectroscopy and Glancing Incidence XRay Diffraction (GIXRD). After the PLM annealing, Ti concentration is over the Mott limit. Nevertheless, the Raman spectra show a forbidden TO vibrational mode of GaP. This result suggests the formation of crystalline domains with a different orientation in the annealed region regarding to the GaP unannealed substrate. This conclusion has been corroborated by GIXRD measurements. As a result of the polycrystalline lattice, a drop of the mobility is produced. INTRODUCTION Intermediate Band (IB) is a highly attractive phenomenon that could be observed in semiconductors highly impurified and could have potential applications for optoelectronic devices [1]. An IB material is formed by the introduction of a new band inside the bandgap of a semiconductor. In these new kind of compounds, photons with energy below the bandgap can be absorbed, pumping electrons from the valence band to the conduction band with the IB as an intermediary step. One way to form an IB material is to introduce deep center impurities with a concentration above the Mott limit (∼5.9x1019 cm-3) in a host semiconductor [2]. If the concentration is high enough the wave functions of the impurity electrons will overlap and a new band will be formed. In this context a reduction of the Shockley-Read-Hall recombination increased by the presence of the deep levels is expected to occur [3]. Theoretical calculations have predicted the formation of an Intermediate Band in GaP impurified with Ti when the concentration of the impurities is above the Mott limit [4,5]. The approach of using high concentration deep level impurities to form an IB in the traditional semiconductors have been intensely researched recently [6 – 9]. Ion implantation is a non-equilibrium technique that permits introducing a Ti impurity concentration above the solubility limit of the Ti in GaP [13]. However, the implantation damages the lattice crystal and post-annealing treatments are required to recover the lattice quality. Pulsed-Laser Melting (PLM) annealing is able to produce supersaturated layers with high crystalline quality [6], avoiding the solid solubility limit that usually restricts the use of common annealing techniques such as rapid thermal annealing. Nonetheless, the effects of PLM annealing in III-V semiconductors
Data Loading...
