Tuning of the electroluminescence from Si nanocrystals through the control of their structural properties
- PDF / 336,316 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 29 Downloads / 208 Views
F11.9.1
Tuning of the electroluminescence from Si nanocrystals through the control of their structural properties A. Irrera1, F. Iacona2, D. Pacifici1, M. Miritello1, G. Franzò1, D. Sanfilippo3, G. Di Stefano3, P.G. Fallica3, and F. Priolo1 1
INFM and Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95123 Catania, Italy; 2CNR-IMM, Sezione di Catania, Stradale Primosole 50, I-95121 Catania, Italy; 3 STMicroelectronics, Stradale Primosole 50, I-95121 Catania, Italy ABSTRACT We have studied the structural, optical and electrical properties of MOS devices, where the dielectric layer consists of a substoichiometric SiOx (x < 2) thin film deposited by plasma enhanced chemical vapor deposition. After deposition the SiOx samples were annealed at high temperature (> 1000°C) to induce the separation of the Si and SiO2 phases with the formation of Si nanocrystals embedded in the insulating matrix. The effects of the Si concentration in the SiOx layer and of the annealing temperature on the electrical and optical properties of these devices are reported and discussed. It is shown that by increasing the Si content in the SiOx layers the operating voltage of the device decreases and the total efficiency of emission increases. In fact, devices having an active layer with high Si concentration (46 at.%) annealed at 1100 °C, exhibit the best performances (i.e. the highest electroluminescence intensity and the lowest operating voltage). Furthermore, we have observed that by decreasing the thickness of the SiOx layer from 75 to 25 nm it is possible to strongly reduce the operating voltage down to 4 V.
INTRODUCTION Silicon has for a long time been considered unsuitable for optoelectronic applications. Due to the indirect nature of its energy band gap, bulk silicon is indeed a highly inefficient light source. Many efforts have been devoted towards the research of different systems compatible with Si technology and able to act as light emitters [1]. Among these, silicon nanocrystals (nc) dispersed in a SiO2 matrix have recently attracted a great interest because their band gap is enlarged with respect to bulk silicon due to quantum confinement effects and an intense visible luminescence (PL) at room temperature is obtained [2-6]. Si nc in SiO2 are produced with several different techniques (mainly, ion implantation [2-4], chemical vapor deposition [5-6], sputtering [7] and laser ablation [8]) but the results obtained have some common features: the PL peak is quite broad due to the size distribution of the nc present in the sample and the PL peak position shifts towards higher energies with reducing the nc size. In spite of the large amount of experimental [2-8] data and theoretical [9-10] calculations present in the literature on the PL properties of Si nanostructures, only a few papers have been reported on the electroluminescence (EL) characteristics of Si nc in SiO2 [11-18], mainly due to the difficulties of carrier injection in a semi-insulating material. Nevertheless the possibility to fabricate an e
Data Loading...
