Papers by Author: J.M. Rafí

Abstract: In order to identify an appropriate low-temperature surface passivation that could be used for bulk lifetime estimation of high resistivity (HR) (> 1 k
·cm) silicon for radiation detectors, different passivating layers were evaluated on n-type and p-type standard Czochralski (CZ), HR magnetic CZ and HR float zone (FZ) substrates. Minority carrier lifetime measurements were performed by means of a μW-PCD set-up. The results show that SiNx PECVD layers deposited at low temperatures (≤ 250°C) may be used to evaluate the impact of different processing steps and treatments on the substrate characteristics for radiation detectors. First results are obtained about a preliminary thermal treatment experiment to evaluate the thermal stability of the passivating layers, as well as the potential impact of the generation of thermal donors on minority carrier lifetime.

Abstract: An overview is given of analytical techniques for the characterization of the electrical and transport parameters in thin (<1 µm) semiconductor layers. Some of these methods have been applied to the lifetime and diffusion length study in thin strain-relaxed buffer (SRB) layers of strained silicon (SSi) substrates, while a second group was dedicated to Silicon-on-Insulator (SOI) materials and devices. The employed techniques can be divided into two groups, whether a device structure (junction, MOS capacitor, MOSFET) is required or not. However, the MicroWave Absorption (MWA) technique can be used in both cases, making it a versatile tool to study both grown-in and processing-induced electrically active defects. The transport properties of SSi wafers are strongly determined by the density of threading and misfit dislocations, although the dependence of the recombination lifetime is weaker than expected from simple Shockley-Read-Hall (SRH) theory. This is related to the high injection regime typically employed, enabling the characterization of the 250-350 nm thick Si1-xGex layer only. At longer carrier decay times, multiple trapping events dominate that can be described by a stretched exponent approach, typical of disordered materials. For SOI substrates, transistor-based techniques will be demonstrated that enable to assess the generation or recombination lifetime in the thin silicon film (<100 nm). The lifetime can be severely degraded by irradiation or hot-carrier degradation. Finally, it will be shown that Generation-Recombination (GR) noise spectroscopy as a function of temperature allows identifying residual ion-implantation-damage related deep levels, which are otherwise hard to detect even by Deep Level Transient Spectroscopy (DLTS).