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The piezophototronic effect has been widely explored to improve the performance of optoelectronic devices. However, modulation of piezoelectric charges varies with different energy band structures. Thus, it is important to investigate the specific role of the piezophototronic effect from a theoretical perspective. Herein, the piezophototronic effect in anisotype p‐Si/n‐ZnO heterojunction photodiodes with type‐II energy band diagrams through analytical derivation and numerical simulation is thoroughly studied. It is found that both the depletion region and quasineutral region have a decisive effect on photocurrent in their respective regions. Specifically, modulations of piezoelectric charges on depletion region current and quasineutral region current are opposite and compensate each other, resulting in reduced piezophototronic effect. Heterojunctions under short diode conditions are preferred for better piezophototronic effect as modulation on quasineutral region current is weakened while that on depletion region current remains unchanged. The effects of doping concentration, absorption coefficient, and minority carrier lifetime of semiconductor materials on device characteristics are also studied. This work provides deeper insight into the underlying device physics of the piezophototronic effect. [ABSTRACT FROM AUTHOR]

Pyroelectricity was discovered long ago and utilized to convert thermal energy that is tiny and usually wasted in daily life into useful electrical energy. The combination of pyroelectricity and optoelectronic yields a novel research field named as Pyro-Phototronic, where light-induced temperature variation of the pyroelectric material produces pyroelectric polarization charges at the interfaces of semiconductor optoelectronic devices, capable of modulating the device performances. In recent years, the pyro-phototronic effect has been vastly adopted and presents huge potential applications in functional optoelectronic devices. Here, we first introduce the basic concept and working mechanism of the pyro-phototronic effect and next summarize the recent progress of the pyro-phototronic effect in advanced photodetectors and light energy harvesting based on diverse materials with different dimensions. The coupling between the pyro-phototronic effect and the piezo-phototronic effect has also been reviewed. This review provides a comprehensive and conceptual summary of the pyro-phototronic effect and perspectives for pyro-phototronic-effect-based potential applications. [ABSTRACT FROM AUTHOR]

The piezotronic effect is a coupling effect of semiconductor and piezoelectric properties. The piezoelectric potential is used to adjust the p-n junction barrier width and Schottky barrier height to control carrier transportation. At present, it has been applied in the fields of sensors, human–machine interaction, and active flexible electronic devices. The piezo-phototronic effect is a three-field coupling effect of semiconductor, photoexcitation, and piezoelectric properties. The piezoelectric potential generated by the applied strain in the piezoelectric semiconductor controls the generation, transport, separation, and recombination of carriers at the metal–semiconductor contact or p-n junction interface, thereby improving optoelectronic devices performance, such as photodetectors, solar cells, and light-emitting diodes (LED). Since then, the piezotronics and piezo-phototronic effects have attracted vast research interest due to their ability to remarkably enhance the performance of electronic and optoelectronic devices. Meanwhile, ZnO has become an ideal material for studying the piezotronic and piezo-phototronic effects due to its simple preparation process and better biocompatibility. In this review, first, the preparation methods and structural characteristics of ZnO nanowires (NWs) with different doping types were summarized. Then, the theoretical basis of the piezotronic effect and its application in the fields of sensors, biochemistry, energy harvesting, and logic operations (based on piezoelectric transistors) were reviewed. Next, the piezo-phototronic effect in the performance of photodetectors, solar cells, and LEDs was also summarized and analyzed. In addition, modulation of the piezotronic and piezo-phototronic effects was compared and summarized for different materials, structural designs, performance characteristics, and working mechanisms' analysis. This comprehensive review provides fundamental theoretical and applied guidance for future research directions in piezotronics and piezo-phototronics for optoelectronic devices and energy harvesting. [ABSTRACT FROM AUTHOR]

The piezo‐phototronic effect has been extensively investigated to improve the performance of optoelectronic devices. However, the modulations in different energy band structures are quite distinctive, and adverse effects may be produced. Therefore, it is essential to investigate the modulation law in the optoelectronic devices with different energy band structures. Here, five kinds of Si/ZnO heterojunction photodiodes (PDs) with different energy band structures are fabricated and the piezo‐phototronic effect is systematically investigated on their photoresponse performance. For the p‐Si/n‐ZnO PDs, significant performance improvement is achieved by the piezo‐phototronic effect, with the magnitude of improvement increasing with doping concentration of p‐Si. For the n‐Si/n‐ZnO PDs, performance improvement is only achieved when the n‐Si is lightly doped, with a lower magnitude compared to that of the p‐Si/n‐ZnO PDs. The in‐depth working mechanism regarding to the different energy band structures is revealed. It is concluded that when the Fermi‐level of Si moves from the bottom of conduction band to the top of the valence band, the magnitude of performance improvement in Si/ZnO heterojunction PD increases. This study not only presents an in‐depth understanding regarding the piezo‐phototronic effect in Si/ZnO heterojunction PDs, but also provides guidance to optimize the piezo‐phototronic effect in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Abstract: The piezo‐phototronic effect is confirmed as a promising methodology to optimize the performance of optoelectronic devices. However, not only positive effects, but also negative effects may be produced in some types of photodiodes (PDs) by the piezo‐phototronic effect, resulting in the restriction of the PDs' photoresponse performance enhancement. In order to obtain the largest possible photoresponse performance enhancement, it is essential to investigate how the piezo‐phototronic effect influences the photoresponse performance of PDs with different device configurations and structures. Here, the piezo‐phototronic effect on the photoresponse performance enhancement of anisotype (p‐Si/n‐ZnO) and isotype (n‐Si/n‐ZnO) heterojunction PDs is thoroughly investigated. The experimental results show that the piezo‐phototronic effect induced improvement of the p‐Si/n‐ZnO heterojunction PD is much larger than that of the n‐Si/n‐ZnO heterojunction PD. The energy band diagrams under compressive strains are carefully analyzed, revealing that two positive effects are introduced to the p‐Si/n‐ZnO heterojunction PD, whereas one positive and two negative effects are introduced to the n‐Si/n‐ZnO heterojunction PD by the piezo‐phototronic effect. This work presents an in‐depth understanding about the piezo‐phototronic effect on the photoresponse performances of PDs with different device configurations and structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effects of substrate temperature and nitrogen to argon ratio on the physical properties of AlN films were studied. • An Au/i-AlN/n-GaN LED was fabricated, and a hole generation model and carrier transport and recombination mechanism were proposed. • The electroluminescence characteristics of Au/i-AlN/n-GaN LED at different temperatures were investigated. Aluminum nitride (AlN) film has a wide range of applications optoelectronic devices. In this paper, AlN thin films were prepared by magnetron sputtering method, the influence of substrate temperature and nitrogen-argon ratio on the structure, morphology and optical properties of AlN films were evaluated by X-ray diffractometer, scanning electron microscope and ultraviolet–visible spectrophotometer. The analysis showed that the AlN film exhibited better crystallization quality under the substrate temperature of 350 °C with a nitrogen-argon ratio of 5:40. In addition, an Au/i-AlN/n-GaN metal–insulator-semiconductor (MIS) structure device was fabricated based on high-quality AlN films. The current–voltage and electroluminescence characteristics of the device under different temperatures were studied in detail. The results showed that the device exhibited excellent rectification behavior at all operating temperatures, producing an intense UV emission (∼372 nm). This paper proposes a hole generation model and a carrier transport and recombination mechanism. The research results provide a new reference for the practical application of AlN films. [ABSTRACT FROM AUTHOR]

The piezophototronic effect is known as a three-way coupling between piezoelectric polarization, semiconductor property, and optical excitation in piezoelectric semiconductor materials to modify their energy band structures by strain-induced piezoelectric polarization charges, and thus to tune/control their optoelectronic processes of charge carrier generation, separation, recombination, and transport. In this work, the temperature dependence of the piezophototronic effect in wurtzite-structured CdS nanowires is investigated from 77 to 300 K. The piezophototronic effect is enhanced by over 550% under lower temperature due to the increased effective piezoelectric polarization surface/interface charges resulting from the reduced screening effect by decreased mobile charge carriers in CdS nanowires. Optoelectronic performances of CdS nanowires are systematically investigated under various light illuminations, strains, and temperatures. By analyzing the corresponding band diagrams, the piezophototronic effect is found to dominate the transport and separation processes of charge carriers. This study presents in-depth fundamental understanding about the piezophototronic effect and provides guidance for its future applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

In x Al 1-x N alloys were prepared on Al 2 O 3 substrates using radio frequency magnetron sputtering. The physical properties of In x Al 1-x N alloys sputtered at different substrate temperatures were systematically studied. The results indicated that the sputtered In x Al 1-x N alloys had c-axis preferred orientation and exhibited phase separation under the substrate temperature over 450 °C. The In content was calculated about 0.62 according to the Vegard's law. It was found that the surface morphology of In 0.62 Al 0.38 N alloys showed a transition from nanodots to nanoclusters and disordered morphology as the substrate temperature was increased from 150 to 450 °C. This research will lay a good foundation for the application of In x Al 1-x N-based optoelectronic devices. • In x Al 1-x N alloys were sputtered by magnetron sputtering at different substrate temperature. • The substrate temperature is critical to effect the physical characteristics of In x Al 1-x N alloys. • The In metal could form good ohmic contact on InAlN alloy surface. • The band gap bending factor b was calculated to be 3.0 eV. [ABSTRACT FROM AUTHOR]

CuO had huge application prospects in the fields of semiconductor optoelectronic devices. However, the preparation of high-quality CuO films was still an urgent problem to be solved. Herein, we prepared CuO films at different sputtering pressures (0.6–2.1 Pa) by magnetron sputtering technology. The experiment results showed that the sputtering pressure had an obvious effect on the optical properties, structure, morphology and electrical properties of CuO films. It showed that relatively better CuO films could be prepared at 1.6 Pa. Moreover, Hall effect indicated that the change of ambient temperature had an obvious effect on the resistivity and carrier concentration of CuO films. Correspondingly, the p-CuO/n-GaN heterojunction device was fabricated, and the relationship between carrier transport characteristics and ambient temperature was studied. Ambient temperature had obvious influence on the turn-on voltage and rectification ratio of the device. This work provided a basis for the practical application of CuO-based optoelectronic devices. • The effect of sputtering pressure on the physical properties of CuO film was studied. • The effect of ambient temperature on the electrical properties of CuO films was studied. • Device with high rectification ratio based on p-CuO/n-GaN structure was prepared. • The influence of operating temperature on the carrier transport properties was studied. [ABSTRACT FROM AUTHOR]

In recent years, GaN materials have been applied to the field of optoelectronic devices due to their excellent photoelectric properties, especially in the field of light-emitting diodes, which has attracted considerable attention. In this article, we use structural engineering methods to further improve the performance of GaN-based ultraviolet light-emitting diodes. The magnetron sputtering and annealing treatment were used to prepare ultraviolet light-emitting diodes based on p-NiO/i-Ga 2 O 3 /n-GaN and p-NiO/n-GaN heterojunction structure. X-ray diffractometer, field emission scanning electron microscope and ultraviolet-visible spectrophotometer were used to study the crystal quality, surface morphology, and optical properties of Ga 2 O 3 film. Compared with the p-NiO/n-GaN heterojunction diode, the p-NiO/i-Ga 2 O 3 /n-GaN heterojunction diode exhibits better rectification characteristics and more excellent electroluminescence characteristics. Under the injection voltage of 35 V, the EL spectrum intensity of p-NiO/i-Ga 2 O 3 /n-GaN heterojunction diode is nearly 37 times higher than that of p-NiO/n-GaN heterojunction diode. Finally, the working mechanism of the electroluminescence is analyzed in detail through the energy band diagram of the two diodes. [ABSTRACT FROM AUTHOR]

The good properties of ITO substrate endow the as-grown InN thin films especially attractive for various optoelectronic applications. Herein, the InN thin films were prepared on the ITO substrates by magnetron sputtering. The effects of substrate temperature (T s) on the structural, morphological, and optical properties of InN films were assessed by X-ray diffractometer, scanning electron microscope and ultraviolet–visible spectrophotometer. The combination of structural and morphological investigation suggested that the better InN thin film was obtained at 200 °C. Then, the variation of the optical band gap and transmittance with T s was discussed. What's more, the p-NiO/n-InN heterojunction was trial-produced, and the carrier transport characteristics were studied in the range of 30–120 °C. The heterojunction exhibited excellent I–V characteristics at all operating temperatures. This work enriches the description of InN materials and devices, and provides a useful reference for the practical application of InN. • High-quality InN thin film was obtained on the ITO substrate by magnetron sputtering. • The increase of substrate temperature was conducive to the growth of InN (101) plane. • High rectification ratio diode based on p-NiO/n-InN structure was trial-produced. • The diode also exhibited superior I–V characteristics under high temperature. [ABSTRACT FROM AUTHOR]