Post-annealing Temperature Research Articles

Synthesis, negative thermal expansion and optical performances of In0.5Sc1.5Mo3O12 thin films via sol-gel spin coating

Orthorhombic In0.5Sc1.5Mo3O12 thin films have been synthesized using the sol-gel spin coating. Influences of post-annealing temperatures on crystal structure, morphology, negative thermal expansion (NTE) and optical performances of the thin films were studied using XRD, SEM, XPS, high-temperature XRD and UV–Vis–NIR spectrophotometer. XRD and SEM results show that as-prepared thin film is in an amorphous state with a smooth and dense surface. Orthorhombic In0.5Sc1.5Mo3O12 thin films were obtained after post-annealing in 550–750 °C. The higher the annealing temperature in 550–750 °C, the better the crystallinity of orthorhombic In0.5Sc1.5Mo3O12 thin films. In addition, the grain size of the In0.5Sc1.5Mo3O12 thin film also grows as the annealing temperature increases. The resulting orthorhombic In0.5Sc1.5Mo3O12 thin films exhibit anisotropic NTE. Its volumetric coefficient of thermal expansion (CTE) is −3.44 × 10−6 °C−1, while the CTEs in a-, b- and c-axis directions are −4.70 × 10−6 °C−1, 5.37 × 10−6 °C−1, and -4.10 × 10−6 °C−1 in 25–700 °C, respectively. In addition, the transmittance of orthorhombic In0.5Sc1.5Mo3O12 thin films post-annealed at 750 °C is around 87.75 %–95.03 %.

Thermal annealing effect on phase evolution, physical properties of DC sputtered copper oxide thin films and transport behavior of ITO/CuO/Al Schottky diodes

Herein, we report on the post-annealing temperature effect on the transport behavior of p-CuO/Al Schottky barrier diodes. In addition, the transformation of phase from Cu4O3 to CuO phase was studied. Copper oxide thin films were grown on soda lime glass substrates, and post-annealing temperature's influence on the films’ structural, chemical, morphological, and electrical characteristics was comprehensively examined. X-ray diffraction study revealed the development of polycrystalline tenorite phase (CuO) on annealing. Raman analysis also confirmed the formation of the tenorite phase (CuO) at higher annealing temperatures (400 °C and 500 °C). XPS study revealed the occurrence of the Cu4O3 phase for room temperature deposited sample and CuO phase at the higher annealing temperature. Using current–voltage analysis, the Chueng model, and the thermoelectric emission model, the Schottky behavior between the metal and semiconductor were investigated. The fabricated diode showed a rectification ratio of 103 at ± 2 V, with the barrier height ranging from 0.84 to 1.12 eV due to different annealing treatments. The attributes of the power law were employed to elucidate space charge-limited conduction and the process of tunneling across the density of interface traps in p-CuO/Al Schottky diodes. This study provides valuable insights into the behavior of the p-CuO/Al Schottky junction, enhancing our understanding of its characteristics.

Annealing effect on physical characterisation and sensing properties of nanostructered AgO thin films

Thermal evaporation (TE)was employed to create thin coatings of AgO on glass substrates. The post-annealing temperatures for the deposited films were (100, 150, and 200), respectively. The XRD data demonstrate that when annealing temperature climbed from 100°C to 200°C, the intensity of (100) plane strengthened. Regardless of the temperatures used for post-annealing, the XRD spectra show that the films are polycrystalline and have a cubic structure. The average grain size was 15.39 nm, 16.30 nm, and 17.68 nm for the intended films. When the annealed temperature rises, the dislocation density and strain value decrease. The root mean square (RMS) roughness measured via AFM images decreased from 7.33 nm to 3.64 nm. Due to annealing at 200°C, the average particle size behaved similarly and reduced from 76.9 nm to 46.5 nm. The surface roughness exhibited the same behavior and dropped from 8.77 nm to 4.46 nm at 200 o C. The sample annealed at 200°C had the highest absorbance values, whereas the sample annealed at 100°C had the highest transmittance values. As the film annealing increased, the absorption coefficient rose somewhat. The bandgap of AgO thin films falls from 1.59 eV to 1.44 eV with the rise of annealing. In contrast, the transmittance, refractive index, and Extinction coefficient also lower as the temperature rises. Sensitivity measurements indicated a reduction in sensitivity as the annealing temperature and gas concentration increased.

Regulating the crystal orientation of vapor-transport-deposited GeSe thin films by a post-annealing treatment

Recently, GeSe has emerged as a highly promising photovoltaic absorber material due to its excellent optoelectronic properties, nontoxicity, and high stability. Although many advantages make GeSe well suited for thin-film solar cells, the power conversion efficiency of the GeSe thin-film solar cell is still much below the theoretical maximum efficiency. One of the challenges lies in controlling the crystal orientation of GeSe to enhance solar cell performance. The two-step preparation of GeSe thin films has not yet been reported to grow along the [111] orientation. In this work, we study the effect of a post-annealing treatment on the GeSe thin films and the performance of the solar cells. It was found that amorphous GeSe films can be converted into polycrystalline films with different orientations by changing the post-annealing temperature. [111]-oriented and [100]-oriented GeSe thin films were successfully prepared on the same substrate by optimizing the annealing conditions. With the structure of Au/GeSe/CdS/ITO cell devices, PCEs of 0.14% and 0.16% were ultimately achieved.

High mobility and hysteresis free InGaSnO thin film transistors by co-sputtering via low temperature post annealing process

In this work, InGaSnO thin film transistors (TFTs) with high mobility (>50 cm2/Vs) were prepared by a simple co-sputtering process at a low temperature of 150 ℃. In the co-sputtering process of InSnO and Ga2O3, the composition of InGaSnO can be reasonably controlled by adjusting the sputtering power in the radio frequency plasma, which significantly affects the electrical performance and stability of InGaSnO TFTs. The highly overlapping 5 s electron cloud of In and Sn and the high binding energy of Sn-O lay the foundation for the high mobility of InGaSnO TFTs. The defects related to oxygen in the channel are suppressed by the reasonable control of the composition of Ga in the multicomponent oxides. Meanwhile, the interface defects between the gate dielectric and the active layer are reduced, and a dense metal-oxygen-metal network is formed which is conducive to electron transmission. We have achieved an InGaSnO TFTs with mobility of 58.7 cm2/Vs and threshold voltage of -1.33 V. The stability under positive and negative bias stress is also significantly improved. In general, a simple co-sputtering process is entirely feasible to realize high-mobility oxide TFTs. The control of the process temperature below 150 ℃ also extends its application in flexible electronic devices.

Ferroelectric polycrystalline Bi2SiO5 thin films on Pt-covered Si substrates prepared by pulsed laser deposition combined with post-annealing

In this study, we report on the fabrication of polycrystalline thin film Bi2SiO5, a notable non-perovskite ferroelectric material. The thin films were deposited on Pt-covered Si substrates by pulsed laser deposition (PLD) at room temperature, followed by a post-annealing process in air. The as-deposited thin film was of an amorphous phase of Bi-Si-O, and turned to a polycrystalline phase of Bi2SiO5 by the post-annealing above 550°C. The influences of the post-annealing temperature on the phase preference, surface morphology, and dielectric properties of the thin films were investigated by Raman spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), and dielectric measurements. As a result, the optimal post-annealing temperature was determined to be 600°C, yielding a good ferroelectric polycrystalline Bi2SiO5 thin film with a relative dielectric constant of 143 and a remanent polarization (2Pr) of 7.2 μC cm−2.

Effect of Oxygen Flow Rate, Post-annealing Temperature, and Different Electrolyte Concentrations on WO3 Thin Films Deposited by DC Magnetron Sputtering For Electrochromic Applications

Effect of Oxygen Flow Rate, Post-annealing Temperature, and Different Electrolyte Concentrations on WO3 Thin Films Deposited by DC Magnetron Sputtering For Electrochromic Applications

Post-annealing in ultra-high vacuum or nitrogen plasma for MoS2 thin films deposited by magnetron sputtering

The thin films of amorphous molybdenum disulfide were deposited at room temperature by magnetron sputtering technique. Post-annealing process in ultra-high vacuum (∼10−8 Pa) or nitrogen plasma environments at the temperatures of 300, 400, 500, and 700 °C have been first proposed to enhance the microstructure and optical properties of MoS2 thin films. The phase transformation of MoS2 thin films from amorphous to polycrystalline was characterized by in situ reflection high-energy electron diffraction during the post-annealing process. The microstructure of MoS2 thin films was also analyzed by Raman spectrum and X-ray diffractometer after the post-annealing process. In addition, the thermal analysis of the differential scanning calorimeter and optical measurement of photoreflectance confirmed the phase transformation of MoS2 thin films. The analysis of photoreflectance also estimated the exciton transition at the bandgap energy of 2.038 eV at 0 K, attributed by the crystalline MoS2 film annealed at 700 °C in ultra-high vacuum. The surface chemical composition of MoS2 thin films has been identified by X-ray photoelectron spectroscopy, but the desulfurization of MoS2 was observed after post-annealing in ultra-high vacuum. Moreover, the preferred orientation of (004) plane in the MoS2 films was performed as the increase in post-annealing temperature.

Surface control of Ni-Al2O3 dry reforming of methane catalyst by composition segregation

Catalyst surface control is of great importance considering that a catalytic reaction initially starts with surface atoms’ interaction with reactant molecules. In the present study, we synthesized the Ni-Al2O3 dry reforming of methane (DRM) catalyst via the spray-pyrolysis-assisted evaporation-induced self-assembly (EISA) method in order to systematically investigate catalyst surface change as controlled by composition segregation. The present results showed that segregation in the Ni-Al2O3 catalyst had successfully occurred by the post-annealing process and that the segregated Ni nanoparticles were located on the catalyst surface with simultaneous reduction to metal. The size of the surface Ni nanoparticles was highly dependent on the post-annealing temperature, whereas the electronic properties did not consistently align with the trend of particle-size growth, indicating that the particle-growth mechanism underwent alterations from segregation to sintering as the temperature was increased. In other words, when the reduction temperature for metal segregation is excessively high, particle-growth on the external catalyst surface, as induced by post-annealing, is primarily attributable to particle sintering rather than to metal segregation. This phenomenon directly results in decreased Ni surface density. The catalytic DRM reaction revealed that due to sintering, the catalytic performance did not align with the trend of Ni particle-size growth, and the conversion of CH4/CO2 was closely associated with Ni surface density. This information will offer valuable insight to future research focused on development of Ni-based catalysts for DRM reactions.

Fabrication of high quality lead-free double perovskite Cs2AgBiBr6 thin film and its application in memristor with ultralow operation voltage

Recently, the lead-free double perovskite Cs2AgBiBr6 has been considered as a promising candidate for next-generation nonvolatile memory and artificial synapse devices due to its high stability and low toxicity compared to its lead-based counterparts. In this work, we developed a simple and effective method to produce high-quality lead-free double perovskite Cs2AgBiBr6 thin films without pinholes and particles by applying a low-pressure assisted method under ambient condition with a relative humidity (RH) of about 45%. The formation of pinholes and Ag precipitation in the perovskite Cs2AgBiBr6 films is effectively suppressed by the proper ratio of N,N-dimenthylformamide (DMF) mixed in dimethyl sulfoxide (DMSO) solvents. Furthermore, the grain size of the Cs2AgBiBr6 films can be significantly increased by increasing the post-annealing temperature. Finally, a sandwiched structure memristor with an ITO/Cs2AgBiBr6/Ta configuration was successfully demonstrated, featuring ultralow operation voltage (V Set ∼ 57 ± 23 mV, V Reset ∼ −692 ± 68 mV) and satisfactory memory window (the ratio of R HRS/R LRS ∼ 10 times), which makes it suitable for low-power consumption information storage devices.

Rapid thermal processing induced interfacial diffusion and solid reaction in the Al2O3/ZnO nano-laminates films

Al2O3/ZnO nanolaminates are promising for thin-film transistors and photoluminescence applications. In this work, the thermal induced interface changes of Al2O3/ZnO nanolaminates were studied as a function of the in site deposition temperature and rapid post-annealing temperature. The Al2O3/ZnO nanolaminates were grown by atomic layer deposition system at 80 °C, 120 °C, and 250 °C, and further post-annealed in a rapid thermal processing (RTP) furnace at 600 °C, 700 °C, and 800 °C for 10 min, separately. Then the microstructures, interfacial diffusion and solid-phase reactions of the Al2O3/ZnO nanolayers were systematically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM). The results show that the in situ growth temperature directly affects the crystallinity and selective orientation of the ZnO interlayers, which further induce the ZnO interlayers to undergo completely different interfacial diffusion and solid-phase reactions during the rapid post-annealing processing. The films grown at 80 °C were close to amorphous, while those grown at 120 °C had a distinctly dominant orientation and exhibited better crystallization at 250 °C. The presence of the ZnAl2O4 grains indicates the solid-phase reactions have occurred on the ZnO/Al2O3 interface during the rapid post-annealing at 700 °C or above.

Post-annealing effect of low temperature atomic layer deposited Al2O3 on the top gate IGZO TFT

Electronical properties of top gate amorphous InGaZnO4 thin film transistors (TFTs) could be controlled by post-annealing treatment, which has a great impact on the Al2O3 insulator. To investigate the effect of post-annealing on Al2O3, Al/Al2O3/p-Si MOS capacitoras with Al2O3 films treated under various post-deposition annealing (PDA) temperature were employed to analysis the change of electrical properties, surface morphology, and chemical components by electrical voltage scanning, atomic force microscope (AFM), and x-ray photoelectron spectroscopy (XPS) technologies. After PDA treatment, the top gate TFTs had a mobility about 7 cm2 V−1 s−1 and the minimum subthreshold swing (SS) about 0.11 V/dec, and the threshold voltage (V th) shifted from positive direction to negative direction as the post-annealing temperature increased. Electrical properties of MOS capacitors revealed the existence of positive fixed charges and the variation of trap state density with increasing PDA temperature, and further explained the change of negative bias stress (NBS) stability in TFT. AFM results clarified the increased leakage current, degraded SS, and NBS stability in MOS capacitors and TFTs, respectively. XPS results not only illuminated the origin of fixed charges and the trap density variation with PDA temperatures of Al2O3 films, but also showed the O and H diffusion from Al2O3 into IGZO during post-annealing process, which led to the deviation of V th, the change of current density, and the negative V th shift after positive bias stress in TFTs.

Sputter grown CuO thin films: Impact of growth pressure and annealing temperature on their microstructural architectures

High-quality copper oxide (CuO) thin films were deposited on the silicon (Si) substrate at the room temperature using the physical vapour deposition (PVD) technique named radio frequency (RF) sputtering. The copper-oxide thin-films were single crystalline and of uniform thickness. Subsequently, the influence of growth pressure (low gas pressure - 3 mTorr and high gas pressure - 100 mTorr) and post growth annealing at different temperatures (300 °C to 700 °C) were investigated to understand the microstructural and morphological changes of the thin film. With the influence of growth pressure and post thermal annealing temperature, significant changes in crystallinity, surface roughness, and surface oxidation rate of the CuO thin film were detected, which were adequately analyzed via several characterization techniques. X-ray diffraction (XRD) patterns revealed the phase formation with good crystallinity of the film, which is substantiated by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) characterization. Atomic force microscopy (AFM) images disclosed that the surface roughness of the film and grain size. By gaining insights into the structural and surface properties of CuO/Si thin films, this research presents new prospects for tuning of CuO phases, structures, and compositions for multifunctional applications.

Influence of annealing temperature on persistent luminescence in BaAl2O4:Eu2+/Eu3+ nanocrystals and its application for latent fingerprint detection.

The luminescent properties of europium (Eu) doped BaAl2O4 phosphors were strongly influenced by post-annealing temperatures for blue-green persistent luminescence and latent fingerprints (LFPs). The X-ray powder diffraction patterns of the BaAl2O4: 1 mol% Eu nanophosphor, annealed between 1000 and 1300 °C, indicated a hexagonal ferroelectric phase. The X-ray photoelectron spectroscopy (XPS) revealed that the Ba atoms occupied two different sites in the BaAl2O4. The XPS and photoluminescence (PL) results revealed the presence of Eu3+ and Eu2+ states. The Eu-doped BaAl2O4 showed the characteristic red emission of Eu3+ at 251 and 464 nm excitations, while excitations at 340 and 380 nm showed yellowish-green emission. Strong evidence of energy transfer between a charge transfer band and the different energy levels of Eu2+ and Eu3+ ions was obtained. The existence of the Cr ion impurity in the aluminates was confirmed with UV-VIS diffuse reflectance and PL spectroscopy. The present results suggested that and O''i defects have introduced electron and hole traps in the host that acted as luminescent centers for persistent luminescence. LFPs detection using BaAl2O3:Eu2+/Eu3+ phosphor showed an excellent marking agent for applications in forensic science.

Influence of oxygen on the optical and electrical properties of magnetron-sputtered indium tin oxide thin films at ambient temperature

Indium Tin Oxide (ITO) thin films are commonly used as transparent conductive layers in the production of solar cells. ITO films are typically heat-treated at temperatures exceeding 200 °C after magnetron sputtering to optimize the physical, optical, and electrical characteristics for photovoltaic devices. This high temperature heating procedure greatly limits the use of potential substrates, particularly those comprised of low-temperature-rated polymers. Herein, we examine the physical, optical, and electrical transport effects of oxygen:argon plasmas during radio frequency magnetron sputtering of ITO on glass and flexible polymer surfaces without subsequent heat treatment. ITO thin films were characterized via sheet resistance testing, UV–Vis spectroscopy, X-ray diffraction, and scanning electron microscopy imaging. Sheet resistance measurements revealed an increase in surface resistance with increasing oxygen concentration during sputtering. UV–Vis optical transmittance measurements demonstrated an improvement in optical transmittance with an increase in oxygen concentration reaching a maximum transmittance at an oxygen concentration of 1-2%. Most importantly, it was discovered that producing bilayers of ITO with pure argon sputtered plasmas followed by oxygen:argon plasmas produced ITO thin films with suitable resistance and transmittance without the need for high temperature post annealing. These results highlight a methodology for the deposition of ITO thin films on temperature sensitive substrates for flexible photovoltaics and low-cost module production.

Optimization of post-annealing temperature for high-performance synaptic transistors based on In–Ga–Zn–O channel and trap layers

Synaptic transistors using an indium–gallium–zinc oxide (IGZO) charge trap layer (CTL) have great potential for high-performance neuromorphic applications due to their excellent stability and high linearity in conductance modulation. Since the high conductivity of the IGZO CTL enhances charge de-trapping performance, the post-annealing process, which directly affects the conductivity of the film, should be carefully conducted. In this study, we investigated the effect of post-annealing temperature (TPA) on the charge de-trapping performance of synaptic transistors. The synaptic transistor showed superior charge de-trapping performance at a TPA of 250 °C, resulting from the increased conductivity of the CTL. Through various electrical and chemical analysis methods, it was revealed that the hydrogen decrease within the CTL and the oxidation–reduction reaction at the interface between the tunneling layer and the CTL contributed to the significant increase in the conductivity of the CTL. The synaptic transistor with the optimal TPA exhibited high linearity of potentiation (αp: 0.56) and depression (αd: −0.65) with 64 conductance levels, enabling the spiking neural network simulation to achieve a high accuracy of 88.75% using a Fashion-MNIST dataset. This work shows that TPA is one of the critical process strategies for the high charge de-trapping performance of the synaptic transistor by inducing the chemical reaction at the CTL interface and hydrogen content change within the CTL.

High-Performance ε-Ga2O3 Solar-Blind Photodetectors Grown by MOCVD with Post-Thermal Annealing

High-temperature annealing has been regarded as an effective technology to improve the performance of Ga2O3-based solar-blind photodetectors (SBPDs). However, as a metastable phase, ε-Ga2O3 thin film may undergo phase transformation during post-annealing. Therefore, it is necessary to investigate the effect of the phase transition and the defect formation or desorption on the performance of photodetectors during post-annealing. In this work, the ε-Ga2O3 thin films were grown on c-plane sapphire with a two-step method, carried out in a metal-organic chemical vapor deposition (MOCVD) system, and the ε-Ga2O3 metal-semiconductor-metal (MSM)-type SBPDs were fabricated. The effects of post-annealing on ε-Ga2O3 MSM SBPDs were investigated. As a metastable phase, ε-Ga2O3 thin film undergoes phase transition when the annealing temperature is higher than 700 °C. As result, the decreased crystal quality makes an SBPD with high dark current and long response time. In contrast, low-temperature annealing at 640 °C, which is the same as the growth temperature, reduces the oxygen-related defects, as confirmed by X-ray photoelectron spectroscopy (XPS) measurement, while the good crystal quality is maintained. The performance of the SBPD with the post-annealing temperature of 640 °C is overall improved greatly compared with the ones fabricated on the other films. It shows the low dark current of 0.069 pA at 10 V, a rejection ratio (Rpeak/R400) of 2.4 × 104 (Rpeak = 230 nm), a higher photo-to-dark current ratio (PDCR) of 3 × 105, and a better time-dependent photoresponse. These results indicate that, while maintaining no phase transition, post-annealing is an effective method to eliminate point defects such as oxygen vacancies in ε-Ga2O3 thin films and improve the performance of SBPDs.

Crystallographic dependence of the electrical transport mechanism in La-Mn-O thermosensitive thin films

Bimetallic oxide materials with amorphous state usually exhibit singular peculiarities due to their periodic disorder structure, implying great potential applications as high-performance electronic devices. In this report, La-Mn-O thin films with different crystallographic features (amorphous and polycrystalline) were deposited on Si (100) substrates using magnetron sputtering method. The as-deposited thin films were successfully convert from the amorphous state to the polycrystalline state by tuning the post-annealing temperatures. X-ray diffraction (XRD) confirmed that La-Mn-O was amorphous at annealing temperatures of 500 °C, while the films were polycrystalline at higher annealing temperatures (600 °C and 700 °C). Scanning electron microscopy (SEM) and high-magnification transmission electron microscopy (HRTEM) distinguished the microscopic features of LaMnO3 thin films in polycrystalline and amorphous states. The effects of annealing temperatures and structural disorder on the temperature-dependent electrical transport properties of La-Mn-O thin films are investigated. The resistance-temperature relationship curves of both polycrystalline and amorphous films show negative temperature coefficient behavior, and the amorphous films follow more than one conduction mechanism. Results show that the electrical transport of the crystalline La-Mn-O films is mainly controlled by thermal activation mechanism, while the electron transport behavior of the amorphous film is simultaneously influenced by thermal activation and Mott VRH variable range hopping conduction.

Macro and nanoscale properties of (001)-oriented Bi0.5Na0.5TiO3 lead-free piezoelectric thin films grown by sputtering on LaNiO3/Si substrates

In this paper, the effect of the post-annealing temperature on the structural and electrical properties at macro and nanoscale of Sodium Bismuth Titanate - Bi0.5Na0.5TiO3 (BNT) films is reported. Stoichiometric BNT thin films were deposited by ex-situ radio frequency (rf) sputtering at substrate temperature of 200 °C. The as-deposited films were amorphous and post-annealing treatment was necessary to crystallize the film in the perovskite phase. 400-nm-thick stoichiometric BNT films were annealed at various temperatures from 400 °C up to 700 °C. The BNT film annealed at 400 °C remains amorphous. Film starts to crystallize at 450 °C and then the crystallization increases with the post-annealing temperature to reach an optimal at 650 °C without any secondary phase. Dielectric, ferroelectric and piezoelectric properties were also improved with the increasing of the post-annealing temperature. The piezoelectric coefficient d33eff, measured at macroscale, reaches a maximum value of 57 pm/V for 400 nm-thick film post-annealed at 650 °C. On nanoscale, measurements performed by piezoresponse force microscopy are in perfect concordance with the performances obtained at macroscale. The efficient polarization reversal for domains and their retention when locally manipulated are observed, combined to a strong piezo-activity.

Enhanced self-driven ultraviolet photodetection performance of high-k Ta2O5/GaN heterostructure

Recently, high-k dielectric oxide-based MIS type ultraviolet (UV) photodetectors (PDs) have engrossed the researchers in the area of optoelectronics owing to their superior properties. The current work focuses on the preparation of symmetric interdigitated Au electrodes on Ta2O5/GaN heterojunction and to check its functioning as a photosensor in UV region. The impact of post-annealing procedure on the bandgap, crystalline quality, surface morphology and chemical composition has been investigated using UV-VIS, XRD, AFM and XPS techniques, respectively. The evaluated optical bandgaps from the Tauc's plots for the Ta2O5 films ranging from 4.52 eV to 4.92 eV. XRD analysis showed the formation of an orthorhombic phase after post-annealing temperature of 700 °C. The post-annealed Ta2O5 film surface morphology comprises prearranged atomic clusters with spherical shapes. The XPS exploration revealed the occurrence of the Ta5+ state and confirmed the formation of Ta2O5 phase. Photodetection parameters of the designed Au/Ta2O5/GaN MIS BB PDs are studied using I–V, responsivity and temporal responses as a function of the post-annealing process. At 0 V bias, with the illumination of 310 nm UV light, the 800 °C post-annealed MIS PD device exhibited peak responsivity of 212 mA/W, external quantum efficiency (EQE) of 86.8 % and detectivity of 1.5 × 1013 Jones. Further, under self-driven mode with 350 nm light illumination, the 800 °C post-annealed UV PD device generated faster rise and fall times of 90 ms and 790 ms, respectively. The post-annealed Au/Ta2O5/GaN heterostructure PD device demonstrates improved photoresponsivity, EQE and rise/fall times compared with the as-deposited PD device. This remarkable improvement in the photodetection performance is attributed to the best band configuration of the Ta2O5/GaN heterostructure because of substantial post-annealing process and facilitating broadband absorption from UV-C to A region with quicker generation, separation and transportation of photogenerated charge carriers. Consequently, the current research work emphasizes the significance of the combination of UV sensing Ta2O5 high-k oxide and n-GaN materials to serve the future necessities of the photodetection technology under self-driven mode i.e., without any external bias.