Renxu Jia

Inhibition of Zero Drift in Perovskite-Based Photodetector Devices via [6,6]-Phenyl-C61-butyric Acid Methyl Ester Doping

Zero drift can severely deteriorate the stability of the light-dark current ratio, detectivity, and responsivity of photodetectors. In this paper, the effects of a [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)-doped perovskite-based photodetector device on the inhibition of zero drift under dark state are discussed. Two kinds of photodetectors (Au/CH3NH3PbIxCl3-x/Au and Au/CH3NH3PbIxCl3-x:PCBM/Au) were prepared, and the materials and photodetector devices were measured by scanning electron microscopy, X-ray diffraction, photoluminescence, ultraviolet absorption spectra, and current-voltage and current-time measurements. It was found that similar merit parameters, including light-dark current ratio (∼102), detectivity (∼1011 Jones), and responsivity were obtained for these two kinds of photodetectors. However, the drift of Au/CH3NH3PbIxCl3-x:PCBM/Au devices is negligible, while a drift of ∼0.2 V exists in Au/CH3NH3PbIxCl3-x/Au devices. A new model is proposed based on the hindering theory of ion (vacancy) migration, and it is believed that the dopant PCBM can hinder the ion (vacancy) migration of perovskite materials to suppress the phenomenon of zero drift in perovskite-based photodetectors.

Temperature-dependence studies of organolead halide perovskite-based metal/semiconductor/metal photodetectors

In this paper, polycrystalline perovskite (CH3NH3PbIxCl3−x) photodetectors with a structure of Au/CH3NH3PbIxCl3−x/Au are prepared and are shown to have good performance. The measured electrical parameters demonstrate that the current behavior of the perovskite photodetectors is dependent of work temperature from 300 K to 350 K. We find that only space charge limited conduction mechanism fits the current–voltage (I–V) curves under small external voltage (0.1–0.7 V) both under darkness and illumination. The lattice vibration scattering plays the major role in the dark, leading to a decreased current as the temperature increases under the same external voltage, and an enlarged current increasing with the temperature is due to the leading role of the ionized impurity scattering. At each temperature, the rising slope of the I–V curves decrease with the increase of voltage both under dark and illumination. The values of on/off ratio, responsivity and detectivity increase with the measured temperature, which indicates that the polycrystalline perovskite photodetector can work with better performance at high temperature. However, the stability in the dark gradually becomes weak as the temperature increases, especially at 330 K and above.

Fabrication of 3.1kV/10A 4H-SiC Junction Barrier Schottky Diodes

A 4H-SiC Junction Barrier Schottky Diodes(JBSs) based on 30μm, 3×10¹⁵ cm^-3 epitaxial structures was fabricated by using metal Ti as the Schottky metal. The Non-linearly limit field rings (NL-FLRs) is used as termination for protecting the anode edge. The fabricated device shows a breakdown voltage of 3.1kV at reverse leakage current of 200uA and the forward current of 11A at the voltage drop of 3 V, corresponding to a current density of 275A/cm², of which the on-resistance is 7.3 mΩ·cm². Finally, the 5266 MW/cm² BFOM value of fabricated SiC JBSs is achieved. The results show our fabricated SiC JBSs has an excellent performance.

4H-SiC Junction Barrier Schottky diode with embedded P-layer

4H-SiC Junction Barrier Schottky diode with embedded P-layer (JBS-EPL) is reported in this paper. JBS-EPL has attractive advantages, such as remarkably increasing the breakdown voltage and decreasing the power loss and die area comparing with conventional Junction Barrier Schottky diode. The estimates for power loss and die area are proposed that can be used for evaluating the different structure design of power devices.

Giant Zero-Drift Electronic Behaviors in Methylammonium Lead Halide Perovskite Diodes by Doping Iodine Ions

Methylammonium lead halide perovskites have attracted extensive attention for optoelectronic applications. Carrier transport in perovskites is obscured by vacancy-mediated ion migration, resulting in anomalous electronic behavior and deteriorated reliability of the devices. In this communication, we demonstrate that ion migration can be significantly enhanced by doping additional mobile I- ions into the perovskite bulk. Ionic confinement structures of vertical metal oxide semiconductor (MOS) and lateral metal semiconductor metal (MSM) diodes designed to decouple ion-migration/accumulation and electronic transport are fabricated and characterized. Measurement conditions (electric-field history, scan rate and sweep frequency) are shown to affect the electronic transport in perovskite films, through a mechanism involving ion migration and accumulation at the block interfaces. Prominent zero-point drifts of dark current-voltage curves in both vertical and lateral diode are presented, and further varied with the perovskite film containingthe different iodine-lead atomic ratio. The doped perovskite has a large ion current at grain boundaries, offering a large ion hysteresis loopand zero drift value. The results confirmthat the intrinsic behavior of perovskite film is responsible for the hysteresisof the optoelectronic devices, but also paves the way for potential applications in many types of devices including memristors and solid electrolyte batteries by doping the native species (I− ions) in perovskite film.

Fabrications and characterizations of high performance 1.2 kV, 3.3 kV, and 5.0 kV class 4H–SiC power SBDs*

In this paper, 1.2 kV, 3.3 kV, and 5.0 kV class 4H–SiC power Schottky barrier diodes (SBDs) are fabricated with three N-type drift layer thickness values of 10 μm, 30 μm, and 50 μm, respectively. The avalanche breakdown capabilities, static and transient characteristics of the fabricated devices are measured in detail and compared with the theoretical predictions. It is found that the experimental results match well with the theoretical calculation results and are very close to the 4H–SiC theoretical limit line. The best achieved breakdown voltages (BVs) of the diodes on the 10 μm, 30 μm, and 50 μm epilayers are 1400 V, 3320 V, and 5200 V, respectively. Differential specific-on resistances (R on−sp) are 2.1 mΩ cm2, 7.34 mΩcm2, and 30.3 mΩcm2, respectively.

Effect of electrical stress on the Al 2 O 3 -based 4H-SiC MOS capacitor with a thin SiO 2 interface buffer layer

The effect of electrical stress on the Al₂O₃-based n-4H-SiC metal oxide semiconductor (MOS) capacitor with a thin SiO₂ interfacial buffer layer (IBL) has been investigated. The electrical characteristics of MOS capacitors have been measured using capacitance-voltage (C-V), current-voltage (I-V) and charge trapping behavior of the films under constant voltage stressing (CVS) to understand the reliability and the interface trapping characteristics of Al₂O₃/SiO₂/n-4H-SiC gate stack. It is found that Al₂O₃/SiO₂ stack layer has lower positive charge generation and smaller flatband voltage shift under constant voltage stressing, which exhibits an excellent interface quality and high dielectric reliability making this structure suitable for 4H-SiC power devices applications.

Reduction of deep level defects in unintentionally doped 4H-SiC homo-epilayers by ion implantation

In order to reduce deep level defects, the theory and process design of 4H-SiC homoepitaxial layer implanted by carbon ion are studied. With the Monte Carlo simulator TRIM, the ion implantation range, location of peak concentration and longitudinal straggling of carbon are calculated. The process for improving deep energy level in undoped 4H-SiC homoepitaxial layer by three times carbon ion-implantation is proposed, including implantation energy, dose, the SiO2 resist mask, annealing temperature, annealing time and annealing protection. The deep energy level in 4H-SiC material can be significantly improved by implantation of carbon atoms into a shallow surface layer. The damage of crystal lattice can be repaired well, and the carbon ions are effectively activated after 1 600 °C annealing, meanwhile, deep level defects are decreased.

Crystallization study for MgO in magnetic tunnel junction structure

The growth and crystallization processes of Co<inf>20</inf>Fe<inf>50</inf>B<inf>30</inf>/MgO/Co<inf>20</inf>Fe<inf>50</inf>B<inf>30</inf> magnetic tunnel junction structures is investigated with 2θ x-ray diffraction. A MgO layer with thickness of 1.5nm was grown on an amorphous CoFeB layer, and then was crystallized. By proper annealing, the crystal structure of MgO has been improved. The results show important information for preparation of magnetic tunnel junction.

Analysis and simulation of inverter employing SiC Schottky diode

The effect of the diode reverse recovery on the performance of inverters is analyzed. The PSpice simulation of the SPWM full bridge inverter has been performed with the Si p-i-n ultra fast diode and the SiC Schottky diode respectively used as the free wheeling diode under the same condition. With their comparison, the results show that the SiC Schottky diode can greatly reduce the power loss of inverters. Further more, the effects of diode parameter CJO on reverse recovery characteristics have been discussed.