Abstract
We report a novel three-terminal device fabricated on MgZnO/ZnO/MgZnO triple-layer architecture. Because of the combined barrier modulation effect by both gate and drain biases, the device shows an unconventional I–V characteristics compared to a common field effect transistor. The photoresponse behavior of this unique device was also investigated and applied in constructing a new type ultraviolet (UV) photodetector, which may be potentially used as an active element in a UV imaging array. More significantly, the proper gate bias-control offers a new pathway to overcome the common persistent photoconductivity (PPC) effect problem. Additionally, the MgZnO:F as a channel layer was chosen to optimize the photoresponse properties, and the spectrum indicated a gate bias-dependent wavelength-selectable feature for different response peaks, which suggests the possibility to build a unique dual-band UV photodetector with this new architecture.
Highlights
The new three-terminal device consists of a tri-semiconductor MgZnO/ZnO/MgZnO layers synthesized on a p-type Si (111) substrate by radio-frequency plasma assisted molecular beam epitaxy
The six-fold symmetrical streaky lines recorded by in-situ reflection high-energy electron diffraction (RHEED) monitor retained in the whole growth process of all sandwiched layers [Fig. 1(b)], indicating that all triple layers in MgxZn1−xO/ZnO/MgxZn1−xO follow a quasi-homo epitaxy mode with the single-phase wurtzite structure and smooth interface morphology[22]
We defined the Von as the Vds that forms a conductive channel between the source and drain electrodes, which lead the Ids change from lower off current to linearly increasing region; and the Vsat as the Figure 2. novel I–V characteristics of our three-terminal device (a) Ids–Vds characteristics of MgZnO/ZnO/ MgZnO/Si field-effect transistor (FET) with Vg increased from 2 V to 10 V in a forward step of 1 V, (b) Ids–Vds characteristics conducted over a range of Vds (0 ~ 15 V) and Vg (−2 ~ 2 V) (c) Ig–Vg characteristics as functions of Vds, and (d) variation of the peaks in transfer curves and turn on voltages in output curves as a function of Vds and Vg, respectively
Summary
From the peak positions indicated by the arrows in the scanning electron microscopy (SEM) image, the thickness of each layer in the tri-layer architecture is ~150 nm, ~72.8 nm, and ~353 nm for top MgZnO, middle ZnO and bottom MgZnO, respectively [Fig. 1(d)] In this stacked structure, the bottom MgXZn1−XO layer was employed as dielectric to allow adjustment of the source to drain current which has been reported in our previous work[22], while the top MgZnO was used to provide Schottky barrier between channel layer and Ti/Au electrode. The bottom MgXZn1−XO layer was employed as dielectric to allow adjustment of the source to drain current which has been reported in our previous work[22], while the top MgZnO was used to provide Schottky barrier between channel layer and Ti/Au electrode It can protect the sandwiched ZnO channel layer from damage during processing
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