This paper describes successfully formed ohmic contacts to 4H-SiC with a view to their use in the technology of bipolar devices. The individual activities included in this investigation were divided into two main parts concerning n-type and p-type silicon carbide processing and different issues have been discussed in relation to that division. In the first part of the experiment titanium-based ohmic contacts to n-type 4H-SiC have been fabricated. The influence of annealing temperature within the range of 850-1100°C and the composition of working gases in RTP reactor on I-V characteristics and contact resistance have been examined. Furthermore, the effect of surface preparation by thermal oxidation of SiC substrate and removal of the oxide immediately prior to contact metallization deposition was investigated. The results obtained for the Si-face (0001) and C-face (000-1) of n-type 4H-SiC were compared. Further research concerns ohmic contacts formation to p-type 4H-SiC based on titanium-aluminum alloys. Four metallization compositions differing in the aluminum layer thickness (25, 50, 75, 100 nm) at a constant thickness of the titanium layer (50 nm) were examined. The structures were annealed within temperature range of 800°C - 1100°C and then electrically characterized. The best electrical parameters and linear, ohmic character of contacts were obtained for structures with Al layer thickness equal or greater then Ti layer thickness and annealing at temperature of 1000°C or higher. Circular Transmission Line Measurement (c-TLM) technique was adopted in both described cases to define a variation in contact resistance (Rc), transfer length (LT), specific contact resistance (ρc) and sheet resistance (Rsh) between metal contacts and silicon carbide.
This paper describes the technology and characterization of HgCdTe photodetectors developed in Vigo System S.A.. Four different variations of devices have been made which include different substrate types and different passivation coatings. CdTe passivation and anodization have been compared. Additionally, both passivations have been strengthened using a negative photoresist SU-8. As fabricated devices have been destined to work as infrared radiation detectors, there has been performed a current measurement for reverse polarization. Based on current-voltage characteristics, current densities have been calculated and compared among fabricated photodiodes to find the best solution of examined passivations.
This paper presents the technological issue of silicon carbide MOSFET design. Through the use of simulations of silicon carbide transistor, the influence of the different the technological parameters are described and discussed. MOSFET transistor was performed in Silvaco TCAD using technology elaborated at Lublin University of Technology. The most important parameters related to ion implantation, which was used in p-i-n photodiode technology. The electrical simulations were performed, transfer and output characteristics for different values of technological parameters were generated – influence of gate oxide thickness on threshold voltage and influence of channel length modulation were checked. The results of simulations as well as transfer and output characteristics allowed to select optimal parameters between expected device working and available technology – gate oxide thickness and transistor channel length were established. This work was in fact carried out to increase our understanding of the device characteristics so as to allow the design of new SiC circuits which could meet the stressful requirements of ultraviolet detector systems.
The rapidly growing demand for electronic devices requires using of alternative semiconductor materials, which could replace conventional silicon. Silicon carbide has been proposed for these harsh environment applications (high temperature, high voltage, high power conditions) because of its wide bandgap, its high temperature operation ability, its excellent thermal and chemical stability, and its high breakdown electric field strength. The Schottky barrier diode (SBD) is known as one of the best refined SiC devices. This paper presents prepared model, simulations and description of technology of 4H-SiC Schottky junction as well as characterization of fabricated structures. The future aim of the application of the structures is an optical detection of an ultraviolet radiation. The model section contains a comparison of two different solutions of SBD’s construction. Simulations – as a crucial process of designing electronic devices – have been performed using the ATLAS device of Silvaco TCAD software. As a final result the paper shows I-V characteristics of fabricated diodes.