Papers by Keyword: Schottky Contact

Abstract: In this work, the electrical properties of Mo₂C/4H-SiC Schottky contacts were studied at different annealing temperatures. In particular, the Schottky barrier height was derived by current-voltage measurements on as-deposited and 400 °C and 700 °C-annealed contacts. The Schottky barrier height was comparable for the as-deposited and 400°C-annealed Mo₂C/4H-SiC contact (0.94 and 0.96 eV, respectively), while it increased (1.07 eV) for the 700 °C-annealed Mo₂C/4H-SiC one. For the sample annealed at 700°C, the electrical characterization of the diodes was combined with the study of the surface and interface electrical properties, by Kelvin-probe force microscopy (KPFM) and frequency dependent capacitance-voltage measurements (C-f-V) and discussed assuming a Mo/4H-SiC Schottky contact (F_B =1.39 eV) as a reference. The KPFM measurements revealed a similar value of the surface potential, thus suggesting that the work function of the metal is the same in both cases. On the other hand, a higher density of interface state was obtained by C-f-V for the Mo₂C/4H-SiC system. This latter can explain the reduction of the Schottky barrier height observed for this system.

Abstract: In this work, we investigated the electrical properties evolution of Mo/4H-SiC Schottky contacts following thermal annealing treatments at temperature up to 950 °C. The electrical characterization under forward and reverse bias revealed a reduction of the barrier height from 1.45 eV (as-deposited contact) to 1.30 eV (950°C-annealed contact), with the presence of inhomogeneity in the contact, while the leakage current followed a thermionic-field emission (TFE) model after annealing at 750 °C and presented a significant increase for the 950°C-annealed contact. The electrical characterization was associated with microstructural analyses, which highlighted an enlargement of the grains forming the structure of the Mo-film and the presence of voids near the Mo/4H-SiC interface. These observations can be at the base of the variation in the electrical behavior of the contact.

Abstract: In this paper, the impact of the anode contact in SBDs, PiN, JBS and MPS diodes is analyzed through TCAD simulations. The focus of the investigation is the correct simulation of the Schottky barrier height on the different areas of the device to correctly simulate a JBS or MPS structure. It is found that the splitting of the anode contact and an accurate selection of the Schottky barrier height on pzone is necessary to allow the onset of the bipolar conduction in MPS devices. In this way, it is possible to correctly analyze the behavior of an MPS diode, including the snapback phenomenon.

Abstract: The paper presents the route of manufacturing transistors on gallium nitride. As a result of the work done, prototypes of transistor crystals with a gate length and width of 0.5 μm and 0.8 mm, respectively. The basic static characteristics are presented.

Abstract: Two characterization methods are compared in terms of their suitability for predicting the electrical behavior of non-uniform Ni/4H-SiC Schottky contacts up to 450°C, using data measured at lower temperatures. These techniques are based on the established Gaussian distribution of barrier heights model and a recently proposed discrete barrier distribution model, respectively. Two samples with different degrees of contact inhomogeneity are measured and their forward characteristics are fitted using both techniques. The Gaussian distribution approach is shown to accurately fit experimental data only for the nearly-uniform sample, while requiring the extraction of two separate barrier height values from measurements in the room-250°C range, only. When attempting to use this method to characterize the sample with strong non-uniformity, fitting accuracy (given by R²) drops under 90%. In contrast, the discrete barrier distribution technique is proven able to forecast the electrical behavior of both samples (with R² > 99% in most cases), over the entire room-450°C range, using a single Schottky barrier for each device (1.61V, corresponding to a Ni₂Si Schottky contact and 0.9V, afferent to a Ni metallization).

Abstract: The physics and technology of metal/semiconductor interfaces are key-points in the development of silicon carbide (SiC) based devices. Although in the last decade, the metal to 4H-SiC contacts, either Ohmic or Schottky type, have been extensively investigated with important achievements, these remain even now an intriguing topic since metal contacts are fundamental bricks of all electronic devices. Hence, their comprehension is at the base of the improvement of the performances of simple devices and complex systems. In this context, this paper aims to highlight some relevant aspects related to metal/semiconductor contacts to SiC, both on n-type and p-type, with an emphasis on the role of the barrier and on the carrier transport mechanisms at the interfaces.

Abstract: ZnO nanowires are recently used in optoelectronic devices such as sensors, solar cells, and light emitting diodes due to its unique optical and electrical properties. In such devices, a contact between the ZnO nanowires and a metal electrode exists. Hence understanding electrical characteristic between the ZnO nanowires and a metal electrode can facilitate optoelectronic device design. In this work, ZnO nanowires were grown on Indium Tin Oxide (ITO) substrates using a hydrothermal method. Simple devices using the nanowires sandwiched between the ITO and a metal contact (i.e. Au, Al) were fabricated and characterized by a current-voltage measurement. Moreover, studies on p-n junctions between the ZnO nanowires and p-type polymers, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) and poly(9,9-dioctylfluorene) (PFO), were also fabricated and characterized. The current-voltage measurement of devices clearly shows the rectifying behavior, which is an important characteristic of diodes.

Abstract: The resistive switching behavior of a low resistive p-type α-Fe₂O₃ thin film sandwiched between Fe bottom electrode and top electrodes of various materials (Fe, Ni and TiN) was studied by current-voltage measurements. When TiN was used for top electrode of memory cell, the reversible resistive switching behavior was observed for over 100 cycles. From impedance measurement, it was suggested that the resistive switching behavior in the TiN/p-type α-Fe₂O₃/Fe device is attributed to the change of the contact resistance in the interface between TiN and α-Fe₂O₃ layers.

Abstract: An AlGaN/AlN ultraviolet photodetector with metal-semiconductor-metal structure is fabricated on n type 4H-SiC substrate, which is conventionally epitaxial by metal-organic chemical vapor deposition (MOCVD). The MSM structure is composed of two interdigitated fingers usually formed by Schottky contact which deposited metal with high work function metal by e-beam metallization and thermal evaporator on high resistance layers. This type of MSM has potential advantages, including ultra low dark current because of its rectifying contacts. The current Characteristics are revealed in this paper. A reference sample of AlGaN/GaN heterostructure with two-dimensional electron gas (2DEG) is also fabricated for comparision.

Abstract: The near-SiC-interfaces of annealed Ni/SiC contacts were observed directly by high-resolution transmission electron microscopy (HRTEM). 1 nm native oxide layer was observed in the as-deposited contact interface. The native oxide layer cannot be removed at 650°C through rapid thermal annealing (RTA) and it was completely removed at 1000°C RTA. The residue of native oxide layer resulted in the Schottky characters. High temperature annealing (>950°C) not only removes the oxide layer in the near-SiC-interface, but also forms a well arranged flat Ni2Si/SiC interface, which contribute to the formation of ohmic behavior.