Transfer Length Method Patterns Research Articles

How to Accurately Determine the Ohmic Contact Properties on n-Type 4H-SiC

The electrical properties of ohmic contacts are classically investigated by using the transfer length method (TLM). In the literature, the TLM patterns are fabricated onto different substrate configurations, especially directly onto the 4H-SiC wafers. But, due to the high doping level of commercial substrates, the current is not confined close to the contact and, in this case, the specific contact resistance (SCR) value is overestimated. In this article, we propose, by the means of simulations, to investigate the influence of the layer under the contact towards the estimation of the SCR. The simulation results highlight that, for an accurate determination of the SCR values, an isolation layer between the contact and the silicon carbide substrate is mandatory. Thus, we have determined the characteristics (doping level and thickness) of a suitable isolation layer compatible with SCR values ranging from 10−3 to 10−6 Ω·cm2.

Via Size-Dependent Properties of TiAl Ohmic Contacts on 4H-SiC

P-type Ti/Al-based contact vias of different sizes but identical processing were electrically characterized using linear transfer length method (TLM) patterns and metal-oxide-semiconductor (MOS) transistors. While the TLM patterns and MOS transistors with large vias follow ohmic contact behavior, Schottky contact properties were observed for smaller contact via dimensions. Focused ion beam (FIB) analysis of the contact vias verified the presence of Ti3SiC2 on large 66 μm x 25 μm contact vias and its absence on smaller 16 μm x 3 μm ones, correlating its absence with the electrical Schottky properties.

Ti/Au 금속과 n-type ZnO 박막의 Ohmic 접합 연구

The Ohmic contact of Ti/Au metals on n-type ZnO thin film deposited on c-plane sapphire substrates by pulsed laser deposition was investigated by TLM (transfer length method) patterns. The Ti/Au metal films with thickness of 35 nm and 90 nm were deposited by electron-beam evaporator and thermal evaporator, respectively. By using the photo-lithography method, the TLM patterns with gaps were formed. To improve the electrical properties as well as to decrease an interface states and stress between metal and semiconductor, the post-annelaing process was done in oxygen ambient by rapid thermal annealing system at temperature of for 1 min. In this study, it appeared that the minimum specific contact resistivity shows about in annealed sample, which may be originated from formation of oxygen vacancies of ZnO during an oxidation of Ti metal at the interface of Ohmic contacts.