Deep levels in p+-n junctions fabricated by rapid thermal annealing of Mg or Mg/P implanted InP

Abstract

In this work, we investigate the deep levels present in ion implanted and rapid thermal annealed ͑RTA͒ InP p ϩ -n junctions. The samples were implanted with magnesium or coimplanted with magnesium and phosphorus. These levels were characterized using deep level transient spectroscopy ͑DLTS͒ and capacitance-voltage transient technique ͑CVTT͒. Seven majority deep levels located in the upper half of the band gap were detected in the junctions by using DLTS measurements, four of which ͑at 0.6, 0.45, 0.425, and 0.2 eV below the conduction band͒ result from RTA, while the origin of the other three levels ͑at 0.46, 0.25, and 0.27 eV below the conduction band͒ can be ascribed to implantation damage. An RTA-induced origin was assigned to a minority deep level at 1.33 eV above the valence band. From CVTT measurements, several characteristics of each trap were derived. Tentative assignments have been proposed for the physical nature of all deep levels.

Electrical characterization of deep levels existing in Mg-Si- and Mg-P-Si-implanted n InP junctions

“…In a previous work [26], we carried out a detailed comparison among unimplanted-unannealed, unimplantedannealed, and singly Mg implanted-annealed InP junctions. In the present work, we focus our attention on Mg-Si co-implanted samples.…”

“…In order to compare experimental results, these curves were recorded at the same temperature for each centre in different samples. We have previously proposed [26] the physical origin and nature of these centres. As for the technological process responsible for their origin, the E2 and E4 levels were induced by the RTA treatment, whereas the E6 and E7 ones had their origin in the implantation process.…”

“…The E4 deep level was related to a layer of indium vacancies induced by the RTA treatment [26]. For the Siimplanted samples, Si atoms can be also located at indium sites in the lattice.…”

“…A tentative physical origin of this trap was associated with implanted Mg atoms which penetrate into the bulk during the RTA treatment [26]. As the Si implantation is deeper than the Mg one (their projected ranges were 4773 Å and 1055 Å, respectively), Mg atoms must go through damaged areas in their RTA-activated inward diffusion.…”

“…One of the main questions about ion implantation is the characterization of the residual damage after annealing in regions located not only near the pn junction plane or at the implanted layer but also deeper into the bulk. In addition to conventional DLTS, the capacitance-voltage transient technique (CVTT) has proved to be a useful method to characterize deep levels existing in semiconductor materials even when DLTS is complicated by systematic distortions [24][25][26]. We have described this technique in detail elsewhere [24].…”