Epitaxial 4H─SiC based Schottky diode temperature sensors in ultra-low current range

In this work, field plate and guard ring edge-terminated Ni/4H-nSiC Schottky barrier diodes (SBD) were fabricated using standard photolithography process. Strange peaks in capacitance–conductance curves, capacitance roll-off, and a high value of ideality factor (η = 1.3) in fabricated SBD were seen as a signature of interface trap states (Nss) at the residual oxide (2.2 nm)/4H-nSiC interface and series resistance (Rs). Schottky capacitance spectroscopic, High–low capacitance–voltage (C–V) and forward-bias current–voltage (I–V) techniques, in the frequency range from 100 Hz to 1 MHz, determines Nss of the order of 1012 cm−2 eV−1 and were found exponentially distributed in the bandgap of SiC. Using Hill–Coleman's method, the density Nss was calculated to be 1.15 × 1015 cm−2 eV−1 at 100 Hz and 7.81 × 1012 cm−2 eV−1 at 1 MHz, which explains the larger value of capacitance at low frequencies. Relaxation times and capture cross sections of Nss were also estimated. Calculated values of Nss were used in a Silvaco simulation that emphasize that bulk level defects present in the SiC also contributes in the experimentally observed strange peaks in C–V characteristics of fabricated SBD. At higher current levels, calculated values of Rs (V, f), confirm an increase of leakage current through residual oxide and describes the capacitance roll-off phenomena in the fabricated SBD.

Capacitance roll-off and frequency-dispersion capacitance–conductance phenomena in field plate and guard ring edge-terminated Ni/SiO2/4H-nSiC Schottky barrier diodes

We report first-principles calculations that clarify the formation energies and charge transition levels of native point defects and carbon clusters in the 4H polytype of silicon carbide (4H-SiC) under a carbon-rich condition. We applied a hybrid functional that reproduces the experimental bandgap of SiC well and offers reliable defect properties. For point defects, we investigated single vacancies, antisites, and interstitials of Si and C on relevant sites. For carbon clusters, we systematically introduced two additional C atoms into the perfect 4H-SiC lattice with and without removing Si atoms and performed structural optimization to identify stable defect configurations. We found that neutral Si antisites are energetically favorable among Si-point defects in a wide range of the Fermi level position around the intrinsic regime, whereas negatively-charged Si vacancies and a positively-charged Si interstitial on a site surrounded by three Si and three C atoms become favorable under n- and p-type conditions, respectively. For C-point defects, neutral C antisites are favorable under intrinsic and n-type conditions, whereas positively-charged C vacancies become favorable under p-type conditions. We also found that a di-carbon antisite is more favorable than a C-split interstitial, which is the most stable form of single C interstitials.

Native point defects and carbon clusters in 4H-SiC: A hybrid functional study

Zinc oxide (ZnO) film was deposited on p-type InP substrate by means of radio frequency magnetron sputtering technique and thus the Au/ZnO/p-InP (MOS) structure was fabricated. The crystal structure and surface morphology of ZnO film deposited on InP were characterized by X-ray diffraction and atomic force microscopy, respectively. The analysis of interface states of the structure is studied using admittance (Y = G + iωC) measurements at room temperature. It is observed that the capacitance and conductance measurements change with frequency. This change is attributed to the presence of interface states. To determine the interface state density (Nss), the high-low frequency (CHF–CLF) capacitance, Hill–Coleman and conductance methods were used. The Nss values obtained from these methods are in agreement with each other. Furthermore, the effect of the series resistance (Rs) on admittance measurements was investigated. Thus, the obtained results suggest that the prepared structure can be used in various electronic applications.

Analysis of interface states in Au/ZnO/p-InP (MOS) structure

The low dark current, high responsivity and high specific detectivity could be preferably achieved in detectors based on junctions, owing to the efficient constraint of carriers. Compared with the other junctions, planar Schottky junctions have simple structures and technological demands and are easy integrated. Herein, in this work, we prepared the β -Ga2O3 thin film by metal-organic chemical vapor deposition method to construct planar Ti/ β -Ga2O3/Ni Schottky photodiode detectors with different on-state resistances. Fortunately, all the devices exhibit state-of-the-art performances, such as responsivity of 175–1372 A W−1, specific detectivity of 1014 Jones and external quantum efficiency of 85700%–671500%. In addition, the dependences of device performances on the on-state resistances indicate that the higher dark currents, photocurrents and photoresponsivities may well be obtained when on-state resistance is smaller, due to the less external power is used to overcome the impendence and condensance at the Ti/ β -Ga2O3 and Ni/ β -Ga2O3 interfaces, but contributing to higher electric current flow both in the dark and under illuminations.

Ultrahigh-performance planar β-Ga2O3 solar-blind Schottky photodiode detectors

This report is on the diameter dependent thermal sensitivity variation trend of Ni/4H-nSiC Schottky barrier diode (SBD) temperature sensors. Scaled SBDs of 2, 1.6, and 1.2 mm in diameter were fabricated using standard photolithography process comprising a field plate and a guard ring as edge terminations on the same epitaxial wafer. Taking into consideration the heat loss and power consumption, the thermal sensitivities of the fabricated SBDs were measured in the current range from 1 μA to 50 pA. The temperature was varied from 273 to 473 K in step of 25 K. An authoritative consequence of the present study is the observed increase in thermal sensitivity with the diameter of the fabricated SBDs. An exhaustive investigation confirms that in all diodes, there exist nanosized patches, which assumed to have different barrier heights and hence ascertained to be the main cause of anomalies in thermal sensitivity variation with diode size. Taking into account the effective area of these patches, theoretically fit...

Diameter dependent thermal sensitivity variation trend in Ni/4H-SiC Schottky diode temperature sensors

Electronic transport in epitaxial 4H–SiC based Schottky diodes modified selectively by swift heavy ions

Tailoring Surface and Electrical Properties of Ni/4H-nSiC Schottky Barrier Diodes via Selective Swift Heavy Ion Irradiation

A mesa type edge termination in planar junction structures has been devised by involving vibrational energy localisation in crystalline medium leading to atomic scale reordering of host atoms on the boundary of enclosed irradiated region. A fabrication process based on selective MeV ion beam irradiation on a square shaped planar abrupt p-n junction is presented to realize semiconductor junction structures with near ideal electrical characteristics. The experimental validation of the process provides compatibility with microelectronics and suits for Schottky diode structures employing silicon carbide (SiC).

https://iopscience.iop.org/article/10.1088/1742-6596/423/1/012057/pdf

Vibhor Kumar

Papers

Diameter dependent thermal sensitivity variation trend in Ni/4H-SiC Schottky diode temperature sensors

Capacitance roll-off and frequency-dispersion capacitance–conductance phenomena in field plate and guard ring edge-terminated Ni/SiO2/4H-nSiC Schottky barrier diodes

Electronic transport in epitaxial 4H–SiC based Schottky diodes modified selectively by swift heavy ions

Tailoring Surface and Electrical Properties of Ni/4H-nSiC Schottky Barrier Diodes via Selective Swift Heavy Ion Irradiation

Selective SHI irradiation for mesa type edge termination in semiconductor planar junction