High Schottky Barrier Research Articles

Essential Effects on the Mobility Extraction Reliability for Organic Transistors

AbstractThe reliability of mobility has come to be a critical issue to the development of new electronics especially for organic electronics, since mobility is typically extracted from field‐effect transistors containing various extrinsic effects and overestimation is popular in the literature. Recently, this issue is emphasized and a reliability factor (r) is proposed by pioneers to gauge the mobility reported. Albeit many factors discussed, how much the extrinsic effects influencerremains unrevealed and a facile solution by using organic transistors is still lacking. Here, it is shown that the widely used extraction method based on the saturation transfer characteristics is sensitive to contact effect and temperature withrdropping to 43%, indeed leading to large mobility overestimation. By contrast, the linear‐regime methods are more reliable particularly the Y‐function method that demonstrates great reliability (r≈ 100%) even for short‐channel transistors at ultralow temperatures. In addition, operating in saturation regime induces ambipolar conduction further deteriorating reliability if contact doping is absent. High Schottky barriers, on the other side, distort device characteristics making extraction impossible. The results of this study reveal that, aside from device optimizations, selecting a right method is essential for reliable and precise evaluation of the carrier mobility by using organic transistors.

(Invited) Material Advances Toward Vertically-Conducting AlGaN Power Transistors

Due to their large bandgaps (≥ 3.4 eV) compared to Si and SiC, AlGaN alloys have superior material properties that are appealing for the next generation of high-voltage power devices. Most notable is that the critical electrical field scales as the bandgap to the 2.0-2.5 power. Thus, diodes employing wide bandgap semiconductors are expected to operate at higher breakdown voltages with thinner and more heavily-doped drift regions, leading to lower resistive losses compared to Si-based devices. Additionally, the formation of AlGaN-based heterojunctions and the utilization of polarization fields offer design options not possible for devices based on materials such as SiC and diamond. Noteworthy demonstrations of high voltage (> 3 kV) PN and Schottky barrier diodes in both GaN and AlGaN alloys confirm the potential of III-Nitride materials for power devices. However, full exploitation of the efficiency gains promised by III-Nitrides for power management systems also requires vertically-conducting transistors for current switching, in addition to diodes. Analogous to power diodes, vertically-conducting power transistors such as D-MOSFETs employ a thick n-type drift layer to stand-off high reverse voltage, but unlike simple PN diodes, have the p-type material limited to spatially defined regions over the surface of the device. “Selective area p-doping” is typically accomplished in SiC and Si devices by implantation and activation of p-type dopants. However, implantation processing in III-Nitride structures has to date only yielded PN junctions that exhibit significantly higher reverse current leakage than continuously-grown PN junctions. Selective-area epitaxial regrowth of p-type material in regions etched into the drift layer offers an alternative to implantation. However, regrown pn junctions on plasma-etched III-Nitrides with low reverse leakage current have not been demonstrated. In this presentation we will discuss the advances in epitaxial p-regrowth for forming pn junctions on inductively-coupled plasma (ICP) etched n-type GaN and Al0.3Ga0.7N drift layers. The role and sources of unintentionally-introduced Si at the regrown interface will be presented. Additionally, approaches to ameliorate damage and defect states introduced by ICP etching through wet-chemical and in-situ reactor thermal treatments prior to p-regrowth will be related to current-voltage characteristics of regrown diodes. While high voltage GaN-based diodes have been fabricated on vertically-conducting GaN substrates, AlGaN-based high voltage diodes with thick drift layers (≥ 5 μm) have been fabricated on AlN and sapphire substrates. The insulating nature of these substrates necessitates planar device geometries that result in high ohmic losses, heating, and degraded device performance. However, the thick drift layer and the smaller lattice constant of AlGaN alloys present significant challenges for realizing vertically-conducting AlGaN power devices on GaN substrates. Here we report a method for fabricating vertically-conducting AlxGa1-xN PN junctions grown on conducting GaN substrates. An n-type GaN substrate is patterned with parallel, sub-micron-wide mesas separated by trenches etched > 0.5 μm deep prior to AlxGa1-xN overgrowth using metal-organic vapor phase epitaxy. We find that growth temperature, V/III ratio, and group-III molar flux can be used to manipulate the crystalline facets formed along the etched pattern prior to AlxGa1-xN coalescence. Using the described process, coalesced planar AlxGa1-xN epitaxial layers were achieved with less than 6 μm of overgrowth for Al mole fractions up to 0.45, which is the highest Al mole fraction reported to date. Cathodoluminescence measurements of an overgrown Al0.3Ga0.7N epilayer indicate that the density of threading dislocations is mid x 108 cm-2 which is similar to that measured for Al0.3Ga0.7N epilayers overgrown on patterned Al0.3Ga0.7N on sapphire. The current-voltage characteristics of vertically-conducting AlGaN PN diodes grown on GaN substrates will be presented. The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency – Energy (ARPA-E), U.S. Department of Energy under the PNDIODES program managed by Dr. Isik Kizilyalli. This work was also supported, in part, by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525

Density functional theory—projected local density of states—based estimation of Schottky barrier for monolayer MoS2

One of the biggest challenges so far in implementing 2D materials in device applications is the formation of a high quality Schottky barrier. Here, we have conducted density functional theory simulations and employed the projected local density of states technique to study the Schottky contact formation between monolayer (ML) MoS2 with different metal electrodes (Mo, W, and Au). Electrode formation on ML MoS2 changes it from intrinsic to a doped material due to metallization, which creates issues in the formation of a good Schottky contact. Amongst the metals studied here, we observe that Mo tends to form the best Schottky barrier with ML MoS2 based on both the vertical and lateral Schottky barrier heights (0.13 eV for the vertical Schottky barrier and 0.1915 eV for the lateral Schottky barrier) and the built-in potential (0.0793 eV). As compared to Mo, Au forms a high-resistance ohmic contact with a much larger vertical barrier height of 0.63 ± 0.075 eV and a negligible built-in potential. It is thus observed that ML MoS2 is very susceptible to strain and pinning of the Fermi level due to metal junction formation. Thus, understanding both the vertical and horizontal Schottky barrier heights along with the built-in potential is critical for designing high performance 2D semiconductor devices.

Design consideration of high voltage Ga2O3 vertical Schottky barrier diode with field plate

Abstract Gallium oxide (Ga2O3) based vertical Schottky barrier diodes (SBDs) were designed for high voltage switching applications. Since p-type Ga2O3 epitaxy growth or p-type ion implantation technique has not been developed yet, a field plate structure was employed in this study to maximize the breakdown voltage by suppressing the electric field at the anode edge. TCAD simulation was used for the physical analysis of Ga2O3 SBDs from which it was found that careful attention must be paid to the insulator under the field plate. Due to the extremely high breakdown field property of Ga2O3, an insulator with both high permittivity and high breakdown field must be used for the field plate formation.

Minority Carrier Injection in High-Barrier Si-Schottky Diodes

In this paper, we investigate the presence of minority carriers and their role in charge carrier transport in silicon (Si) Schottky diodes with a high potential barrier. Using TCAD simulations along with an analytical model, we show that an inversion charge is induced at the metal–semiconductor (MS) interface in a high-barrier Schottky diode which imparts bipolar-type current characteristics to otherwise a unipolar Schottky diode, even at low-injection operation. In such a high-barrier diode, minority diffusion also becomes important along with the majority carrier thermionic emission and therefore cannot be neglected, unlike in a conventional Schottky diode. The presence of minority carriers at low injection in a high-barrier Si Schottky diode has been experimentally verified via a prior-reported two-diode electrical test method, reverse recovery measurements, and by measuring infrared electroluminescence. It is also shown, via TCAD simulations, that the diffusion component becomes more pronounced in case of a reduced Gummel number and at elevated temperatures.

Three-Phase Morphology Evolution in Sequentially Solution-Processed Polymer Photodetector: Toward Low Dark Current and High Photodetectivity.

Sequentially solution-processed polymer photodetectors (SSP PPDs) based on poly(3-hexylthiophene-2,5-diyl) (P3HT)/[6,6]-phenyl C71-butyric acid methyl ester (PC71BM) are fabricated by depositing the top layers of PC71BM from an appropriate cosolvent of 2-chlorophenol (2-CP)/o-dichlorobenzene (ODCB) onto the predeposited bottom layers of P3HT. By adjusting the ratio of 2-CP/ODCB in the top PC71BM layers, the resulting SSP PPD shows a decreased dark current and an increased photocurrent, leading to a maximum detectivity of 1.23 × 1012 Jones at a wavelength of 550 nm. This value is 5.3-fold higher than that of the conventional bulk heterojunction PPD. Morphology studies reveal that the PC71BM partially penetrates the predeposited P3HT layer during the spin-coating process, resulting in an optimal three-phase morphology with one well-mixed interdiffusion P3HT/PC71BM phase in the middle of the bulk and two pure phases of P3HT and PC71BM at the two electrode sides. We show that the pure phases form high Schottky barriers (>2.0 eV) at the active layer/electrodes interface and efficiently block unfavorable reverse charge carrier injection by significantly decreasing the dark current. The interdiffussion phase enlarges the donor-acceptor interfacial area leading to a large photocurrent. We also reveal that the improved performance of SSP PPDs is also due to the enhanced optical absorption, improved P3HT crystallinity, increased charge carrier mobilities, and suppressed bimolecular recombination.

High Gain β-Ga2O3 Solar-Blind Schottky Barrier Photodiodes via Carrier Multiplication Process

β-Ga2O3, which is a ultra-wide band-gap semiconductor, is an attractive material for next-generation solar-blind photodetectors. A high gain solar-blind Schottky barrier photodetector using an exfoliated single crystalline β-Ga2O3 nano-layer was demonstrated by employing internal carrier multiplication process. Excellent spectral selectivity with high responsivity was obtained between UV-A and UV-C wavelengths with fast response/decay characteristics. The gain of our β-Ga2O3 solar-blind PD was ∼3.78 × 103 under the multiplication mode at the reverse bias of −60 V, where the peak electric field was estimated to be 4.3 MV/cm (equivalent to impact ionization coefficient of 5 × 103 cm−1). Compared with non-multiplication mode, outstanding photo-sensing performances were achieved under the multiplication mode, including a responsivity of 8.18 A/W, a photocurrent-to-dark-current ratio of ∼103 and external quantum efficiency of ∼4 × 103%. High gain via carrier multiplication process in a β-Ga2O3 photodiode proposes a new route toward high performance solar-blind deep-UV photodetectors.

One-step hydrothermal synthesis of peony-like Ag/Bi2WO6 as efficient visible light-driven photocatalyst toward organic pollutants degradation

Here, we report a simple approach to fabricate 3D hierarchical peony-like Ag/Bi2WO6 hybrid photocatalyst through one-step hydrothermal method with l-leucine as a template. The morphology and structure of the resultant materials were characterized by various analytical methods, such as X-ray diffraction, field emission scanning electron microscopy and UV–Vis diffuse reflectance spectra. The photocatalytic performance of Bi2WO6 and Ag/Bi2WO6 samples was evaluated by degrading organic dye and antibiotic in water under visible light irradiation. A series of results indicated that loaded Ag nanoparticles significantly improve the photocatalytic activity of Bi2WO6. In addition, the possible mechanism was proposed that the enhanced photocatalytic activity was resulted from the unique configuration of peony-like morphology that favorable for the adsorption of organic compounds and the high Schottky barriers between interface of Ag NPs and Bi2WO6, which promoted the transfer of photogenerated electrons from Bi2WO6 to Ag NPs. Meanwhile, noble metal Ag can induce surface plasmon resonance leading to the better visible light absorption of Bi2WO6.

Ir/Al multilayer Gates for High Temperature Operated AlGaN/GaN HEMTs

The fabrication and characterization of the sequentially evaporated Ir/Al multilayer gates of AlGaN/GaN circular high electron mobility transistors formed by high temperature oxidation is reported. Annealing at temperature of 800 °C, for 60 s in O2 ambient makes possible to form a sharp gate interface with a high Schottky barrier height at RT (φb = 1.2 eV). It is also shown that high temperature oxidation can be an effective approach in reducing of both the gate and drain leakage currents of high electron mobility transistors (more than six orders). A comprehensive microstructural, electrical, and electro‐thermal characterization of the Ir/Al gates is carried out to study the thermal stability of the gate interface and high temperature performance of the devices. Stable operation of the devices with multilayer Ir/Al gates in the temperature range up to 500 °C is demonstrated. Here, it is proposed that the thermal stability of the interface is controlled by the formed aluminum oxide interfacial layer. Finally, perfectly clear pinch‐off characteristics and thermally induced threshold voltage (Vth) instability as low as −0.58 mV °C−1 are achieved.

Electrical Characteristics of 10-kV 4H-SiC MPS Rectifiers with High Schottky Barrier Height

This paper reports the study of the fabrication and characterization results of 10-kilo-volt (kV) 4H-SiC merged PiN/Schottky rectifiers. A metal contact process was developed to make the Schottky contact on n-type SiC and ohmic contact on p-type SiC at the same time. The diodes with different Schottky contact width were fabricated and characterized for comparison. With the improvement quality of the Schottky contact and the passivation layer, the devices show low leakage current up to 10 kV. The on-state characteristics from room temperature to elevated temperature (423 K) were demonstrated and compared between structures with different Schottky contact width.

Pt Gate Sink-In Process Details Impact on InP HEMT DC and RF Performance

A Pt/Ti/Pt/Au gate electrode stack is commonly used in AlInAs/GaInAs/InP high electron mobility transistors due to the high Schottky barrier height of Pt on AlInAs and the fact that Pt can be controllably diffused through semiconductor layers thereby enabling vertical scaling. We show here that the Pt-AlInAs reaction is not only controlled by the annealing time and temperature—the annealing ambient and the thermal ramp rate also affect the diffusion of Pt through the underlying semiconductor layers and impact the DC and RF device performance. Following the gate metal deposition, one process split was rapid thermal annealed at 250 °C and subsequently passivated by atomic layer deposition (ALD) at 180 °C. For the second process split, the Pt gate sink-in process was carried out in the ALD system at 250 °C simultaneously with the gate passivation. Despite identical gate sink-in temperatures, the two process splits exhibit different characteristics suggesting different gate-to-channel distances. The distance of the Pt gate to the GaInAs channel was therefore confirmed through high-resolution cross-sectional scanning transmission electron microscopy analysis. The results presented here reveal that both the suitable ramp rate and the sink-in ambient are necessary to achieve a fully sunken Pt gate.

Demonstration of AlN Schottky Barrier Diodes With Blocking Voltage Over 1 kV

This letter reports the first demonstration of 1-kV-class AlN Schottky barrier diodes on sapphire substrates by metal organic chemical vapor deposition. The device structure mimics the silicon-on-insulator (SOI) technology, consisting of thin $n$ -AlN epilayer as the device active region and thick resistive AlN underlayer as the insulator. At room temperature, the devices show outstanding performances with a low turn-ON voltage of 1.2 V, a high ON/OFF ratio of $\sim 10^{5}$ , a low ideality factor of 5.5, and a low reverse leakage current below 1 nA. The devices also exhibit excellent thermal stability over 500 K owing to the ultra-wide bandgap of AlN. The breakdown voltage of the devices can be further improved by employing field plate, edge termination technologies, and optimizing the SOI-like device structure. This letter presents a cost-effective route to high performance AlN-based Schottky barrier diodes for high-power, high-voltage, and high-temperature applications.

Device characteristics of enhancement mode double heterostructure DH‐HEMT with boron‐doped GaN gate cap layer for full‐bridge inverter circuit

AbstractThis paper reports a systematic theoretical study of Al0.23Ga0.77N/GaN/AlxGa1‐xN double‐heterojunction high electron mobility transistors (DH‐HEMTs) with a boron‐doped GaN cap layer under the gate. Boron containing GaN is a desired replacement for Schottky gate in DH‐HEMT to improve the resistivity and surface qualities of GaN cap with good structural properties, and the influence of polarization field in the GaN cap layer can be used to lift up the conduction band for normally OFF operation of the device. This study shows that the B‐doped GaN cap layer offers excellent device characteristics such as high threshold voltage VT of 1.92 V, steep subthreshold slope of ~ 72 mV/dec, high ON/OFF drain current ratio of ~ 107, extremely low subthreshold drain current Ids,LL ~ 10−9 A/mm, and low gate leakage current, Igs,LL less than 10−15 A/mm. For an Al0.07Ga0.93N back‐barrier/buffer, a high OFF‐state breakdown voltage (VBR,OFF) of 865 V is achieved at Ids = 1 mA/mm and Vgs = 0 V with substrate grounded and gate‐to‐drain distance and gate field plate length of 10 and 5 μm, respectively. The simulated high VT and VBR,OFF values are achieved due to the presence of increased back‐barrier height of the AlxGa1‐xN buffer and high Schottky barrier between the Boron‐doped GaN cap and gate metal. Finally, a DC to AC full‐bridge inverter circuit is designed to evaluate the benefit of B‐doped DH‐HEMTs based switching devices for an ultra‐low‐loss inverter circuit.

Dielectric Properties and Nonohmic Behaviors of CaCu3Ti4O12 Ceramics Prepared by Sol-Gel Process

A sol-gel process was used to synthesize gel precursor of CaCu3Ti4O12. The dry gel were calcined at 800℃/10h and 900℃/10h respectively, and then sintered in air at 1050℃ for 8h. The XRD patterns for calcined powder show that the second phases are contained, and the content of second phases for the powder calcined at 900℃ decreases drastically compared with the powder calcined at 800℃. However, all the second phases have disappeared after the sintering process for the pellets at the same conditions (1050℃/8h, air). The SEM results indicate that the existence of second phases is not conductive to the growth of grains and the formation of grain boundaries during the sintering process. The electric properties measurement demonstrates that the ceramics formulated from dry gel calcined at 900℃/h show not only larger permittivity values and lower dielectric loss, but also larger nonlinear coefficient values comparing those formulated from dry gel calcined at 800℃/h. The nonohmic behaviors measurement results suggest that the higher Schottky barrier is the main factor inducing the larger nonlinear coefficient.

Ambipolar MoS2 Transistors by Nanoscale Tailoring of Schottky Barrier Using Oxygen Plasma Functionalization.

One of the main challenges to exploit molybdenum disulfide (MoS2) potentialities for the next-generation complementary metal oxide semiconductor (CMOS) technology is the realization of p-type or ambipolar field-effect transistors (FETs). Hole transport in MoS2 FETs is typically hampered by the high Schottky barrier height (SBH) for holes at source/drain contacts, due to the Fermi level pinning close to the conduction band. In this work, we show that the SBH of multilayer MoS2 surface can be tailored at nanoscale using soft O2 plasma treatments. The morphological, chemical, and electrical modifications of MoS2 surface under different plasma conditions were investigated by several microscopic and spectroscopic characterization techniques, including X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), conductive AFM (CAFM), aberration-corrected scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). Nanoscale current-voltage mapping by CAFM showed that the SBH maps can be conveniently tuned starting from a narrow SBH distribution (from 0.2 to 0.3 eV) in the case of pristine MoS2 to a broader distribution (from 0.2 to 0.8 eV) after 600 s O2 plasma treatment, which allows both electron and hole injection. This lateral inhomogeneity in the electrical properties was associated with variations of the incorporated oxygen concentration in the MoS2 multilayer surface, as shown by STEM/EELS analyses and confirmed by ab initio density functional theory (DFT) calculations. Back-gated multilayer MoS2 FETs, fabricated by self-aligned deposition of source/drain contacts in the O2 plasma functionalized areas, exhibit ambipolar current transport with on/off current ratio Ion/Ioff ≈ 103 and field-effect mobilities of 11.5 and 7.2 cm2 V-1 s-1 for electrons and holes, respectively. The electrical behavior of these novel ambipolar devices is discussed in terms of the peculiar current injection mechanisms in the O2 plasma functionalized MoS2 surface.

High temperature operation of n-AlGaN channel metal semiconductor field effect transistors on low-defect AlN templates

We report room-temperature to 200 °C operation of n-Al0.65Ga0.35N channel metal semiconductor field effect transistors (MESFET) grown over high-quality AlN/sapphire templates. For this temperature range, the source-drain currents, threshold voltages, and dc-transconductance values remain nearly unchanged with an estimated field-effect mobility of ∼90 cm2/V-s at 200 °C and currents of >100 mA/mm. The analysis of the temperature dependent current-voltage characteristics of the gate-source Schottky barrier diode reveals that the leakage currents arise from Frenkel-Poole emission. The capacitance-voltage data show no hysteresis, indicating a high quality Schottky barrier interface. These MESFET's have excellent potential for use as a high temperature power electronic or a solar-blind ultraviolet sensing device.

Nearly ideal vertical GaN Schottky barrier diodes with ultralow turn-on voltage and on-resistance

Vertical Schottky barrier diodes (SBDs) were fabricated from the metal–organic chemical vapor deposition (MOCVD)-grown GaN epitaxial layer on free-standing GaN substrates. It was found that the quality of GaN drift layers and SBD properties were strongly dependent on the growth rates. The step-flow surface morphology, near-unity ideality factor (n ∼ 1.04), and high Schottky barrier height (∼0.97 eV) were achieved at a relatively low growth rate of 2.61 µm/h. An extremely low turn-on voltage (0.73 V), together with a low on-resistance of 0.72 mΩ·cm2, was obtained.

Conductive and Stable Magnesium Oxide Electron‐Selective Contacts for Efficient Silicon Solar Cells

A high Schottky barrier (>0.65 eV) for electrons is typically found on lightly doped n‐type crystalline (c‐Si) wafers for a variety of contact metals. This behavior is commonly attributed to the Fermi‐level pinning effect and has hindered the development of n‐type c‐Si solar cells, while its p‐type counterparts have been commercialized for several decades, typically utilizing aluminium alloys in full‐area, and more recently, partial‐area rear contact configurations. Here the authors demonstrate a highly conductive and thermally stable electrode composed of a magnesium oxide/aluminium (MgOx/Al) contact, achieving moderately low resistivity Ohmic contacts on lightly doped n‐type c‐Si. The electrode, functionalized with nanoscale MgOx films, significantly enhances the performance of n‐type c‐Si solar cells to a power conversion efficiency of 20%, advancing n‐type c‐Si solar cells with full‐area dopant‐free rear contacts to a point of competitiveness with the standard p‐type architecture. The low thermal budget of the cathode formation, its dopant‐free nature, and the simplicity of the device structure enabled by the MgOx/Al contact open up new possibilities in designing and fabricating low‐cost optoelectronic devices, including solar cells, thin film transistors, or light emitting diodes.

Si-Schottky Photodetector Based on Metal Stripe in Slot-Waveguide Microring Resonator

We present a novel Schottky contact photodetector (PD) based on internal photoemission effect (IPE) comprising of a straight air-slot-waveguide (WG) and a metal/silicide stripe buried in a p-type Si microring resonator (MRR) for optical communication. Several metal/silicides are considered for the stripe (PtSi, Pd2Si, TaSi2, and Ag). This PD benefits from the essential features of slot-WGs, MRR-based PDs, and double Schottky barrier (DSB) PDs. For a TaSi2 PD using DSB S-WG-MRR with high Schottky barrier feature, numerical simulation predicts the responsivity of $\sim 0.22$ A/W, a bandwidth-efficiency product of $\sim 10.5$ GHz, and a dark current of 30 pA at room temperature. These characteristics are significantly improved in comparison with those reported for MRR-IPE-PDs.

Dual Extraction of Photogenerated Electrons and Holes from a Ferroelectric Sr0.5Ba0.5Nb2O6 Semiconductor.

The separation of photogenerated charges is a critical factor in photocatalysis. Recently, anomalous photovoltaic (APV) field effects (Voc ∼ 10(3) V/cm) in ferroelectrics, with their strong driving force for charge separation, have attracted much attention in photocatalysis and photoelectrocatalysis. However, it is still unknown whether photogenerated electrons and holes can be simultaneously extracted by the strong driving force toward the surface of ferroelectrics and can become available for surface reactions. This issue becomes critically important in photocatalysis because the surface reaction utilizes both the electrons and holes that reach the surface. In this work, a model lateral symmetric structure, metal/Sr0.5Ba0.5Nb2O6/metal (metal = Ag or Pt), as an electrode was fabricated. The dual extractions of photogenerated electrons and holes on the two opposite metal electrodes were achieved, as revealed by photovoltaic and ferroelectrical hysteresis measurements and photoassisted Kelvin probe force microscopy (KPFM). It was found that the high Schottky barriers of the two opposite Sr0.5Ba0.5Nb2O6-Pt electrodes are key factors that alter the two space charge regions (SCRs) by a poling effect. The resulting built-in electrical fields with parallel directions near both electrodes significantly enhance the charge separation ability. Our model unravels the driving force of charge separation in ferroelectric semiconductors, thus demonstrating the potential for highly efficient charge separation in photocatalysis.