Yuqiang Li

In this letter, we successfully prepared tunable bandgap ZrGaO films on n-GaN substrates by RF magnetron sputtering. ZrGaO films with different Zr contents were successfully prepared with Zr target sputtered with various RF powers and Ga ₂ O ₃ target sputtered with an RF power of 100 W. The bandgap of ZrGaO film deposited with a Zr target sputtering power of 70 W was broadened to 5.4 eV, indicating that Zr can be a promising candidate to enlarge the bandgap of Ga ₂ O ₃ . Based on this ZrGaO film, a deep-ultraviolet photodetector was fabricated, which has an ultrahigh photo-to-dark ratio up to 10 ⁴ and a high responsivity (0.035 A/W at 0 V bias). The proposed idea of preparing bandgap tunable ZrGaO film by alloying ZrO ₂ with Ga ₂ O ₃ is of great significance to the bandgap engineering of Ga ₂ O ₃ and to its application in ultraviolet detection.

In this letter, amorphous silicon nitride (Si3N4) film grown by inductively coupled plasma chemical vapor deposition (ICPCVD) method is used as the photosensitive layer of deep ultraviolet (DUV) detection, whose thickness and roughness are 200 nm and 0.92 nm, respectively. The transverse symmetrical photoconductive detector with interdigital electrodes spacing of 4 μm is fabricated by photolithography, exhibiting ultrahigh photo-to-dark current ratio (PDCR) more than 105, fast fall speed of 127 ms and also a satisfying responsivity of 1.09 mA/W. This work lays a foundation for further researches on Si3N4 in photonics and electronics.

Boron nitride (BN) has attracted substantial attention in the fields of vacuum-ultraviolet (VUV) photodetection owing to its ultra-wide bandgap and high optical absorption coefficient. However, in practical application, boron nitride crystals cannot satisfy current requirements in size and quality. In this work, we prepared an amorphous sp² bonding BN film by magnetron sputtering with boron as the growth source at a low temperature (500 °C). No harsh conditions of high temperature and pressure are required, but the purity and uniformity of the film can be ensured by this method. Based on such a film, a VUV photodetector (PD) with metal–semiconductor–metal (MSM) structure is further constructed, which exhibits an extremely low dark current (∼10⁻¹⁴ A), a high photo-to-dark ratio (∼10³), and an excellent spectrum selectivity of VUV band. The improvement of PD's performance benefits from the pure and compact composition of the grown BN film. These results indicate that the growing amorphous BN film at a low temperature by reactive magnetron sputtering is a feasible method for preparing high-performance BN VUV photodetectors.

For a practical photodetector, fast switching speed and high on-off ratio are essential, and more importantly, the integration capability of the device finally determines its application level. In this work, the judiciously engineered Si₃N₄/Si detector with an open-circuit voltage of 0.41 V is fabricated by chemical vapor deposition methods, and exhibits good performance with repeatability. The advanced integration technology of Si₃N₄ and Si is the foundation for imaging functions in the near future. Compare to the current commercial Si p-i-n photodiodes, the detector cuts off the long-wavelength UV light over 260 nm, realizing the spectrum selectivity without filters or complexed accessories. The stability of this detector is further characterized by cycling response, temperature and light intensity dependence tests. In addition, we also analyze and explain the inherent mechanisms that govern the different operations of two types of Si₃N₄/Si photodetectors.

In-plane enhanced epitaxy provides reference for the preparation of high-quality AlN and development of VUV photodetectors..

A new strategy of constructing an additional heterojunction on the surface of epitaxially grown Ga₂O₃ film with a distorted lattice is proposed to solve the problem of low external quantum efficiency (EQE) in traditional Ga₂O₃ heterojunction photovoltaic devices. Experimentally, an organic–inorganic hybrid poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate/Ga₂O₃/p‐type Si solar‐blind ultraviolet (SBUV) photovoltaic detector is constructed to achieve an ultrahigh EQE of ≈15% at 0 V bias, which is 1–2 orders of magnitude higher than that of the Ga₂O₃ photovoltaic devices reported previously. Here, an enhanced mechanism of photogenerated carrier separation efficiency induced by dual built‐in fields is proposed to explain the high EQE of Ga₂O₃ SBUV photovoltaic devices. In addition, the organic–inorganic hybrid detector displays a high SBUV–visible rejection ratio (R_{255 nm}/R_{405 nm} of ≈450) and fast response speed (rise time of 60 ms and decay time of 88 ms). All these results indicate that the strategy proposed could provide reference for the fabrication of high‐performance Ga₂O₃ SBUV photovoltaic detectors.

Graphene (Gr) has been widely used as a transparent electrode material for photodetectors due to its high conductivity and high transmittance, in recent years. However, the currently low-efficiency manipulation of Gr has hindered the arraying and practical use of such detectors. We invented a multi-step method of accurately tailoring graphene into interdigital electrodes, for fabricating a sensitive, stable deep-ultraviolet photodetector based on Zn-doped Ga2O3 films. The fabricated photodetector exhibits a series of excellent performance, including extremely low dark current (~10-11 A), ultra-high photo-to-dark ratio (>105), satisfactory responsivity (1.05 A/W) and excellent selectivity for DUV band, compared to those with ordinary metal electrodes. The raising of photocurrent and responsivity is attributed to the increase of incident photons through Gr, and separated carriers caused by the built-in electric field formed at the interface of Gr and Ga2O3:Zn films. The proposed ideas and methods of tailoring Gr can not only improve the performance of devices, but more importantly, it contributes to the practical development of graphene.

Vacuum-ultraviolet (VUV) detector equipped on satellites has extensive application in space exploration and cosmic science. For VUV detector, a semiconductor material with sufficiently wide band gap is eagerly desired. In this work, a wide-band-gap amorphous-MgGaO (a-MGO) film was epitaxially grown on n-type GaN substrate by atomic layer deposition and a p-i-n type heterojunction device for VUV detection was constructed with a-MGO film as photosensitive layer and p-type graphene as transparent conductive layer. The device exhibits a good spectral selectivity of VUV with photovoltaic response, a high responsivity (2 mA•W^-1) under zero bias and an ultrafast response speed (rise time of 4.98 μs and decay time of 1 ms) under nanosecond VUV pulse irradiation. This newly developed device shows great potential in VUV detection for space exploration.