Large-scale Ga₂O₃ solar-blind ultraviolet photodetector arrays are essential for achieving high-resolution imaging. In this paper, a 128×128 nMOSFET array with a row-column addressing topology is fabricated on β-Ga₂O₃ grown by atomic layer deposition technology. The array has an area of 25.6 × 25.6 mm², with a single pixel size of 170 × 200 μm².The MOSFET within a single pixel features an effective channel length of 30 μm, a channel width of 90 μm, a 25-nm-thick Al₂O₃insulating layer, a 90-nm-thick β- Ga₂O₃ active region, and a source-to-gate spacing of 10 μm.
Under conditions of dark and 254 nm solar-blind UV illumination with a power density of 3000 μW/cm², MOSFETs are measured using a B1505A semiconductor parameter analyzer. The device exhibits the typical nMOSFET output characteristics, with dark current I_Dd showing a transition from the linear region to the saturation region, and the current value being in the range of several tens of nA. Under the saturation region of V_D=V_G= 10 V, the device displays a large photocurrent I_Dp of over 40 μA. The rising response time τ_r and falling response time τ_f of device are 1755 ms and 82 ms respectively. The long τ_r is attributed to the large photocurrent which depends on the accumulation of photogenerated electrons. The accumulation of high concentration of generated electrons in the channel and their transport process within the channel result in the prolongation of the rising process.
Further, a representative area sampling method is adopted to evaluate the current consistency performance of the 128×128 array. One 10×10 pixel sub-region is selected from each of the four corner areas, the four edge center areas, and the center area of the array, respectively, and defined as regions A1 to A9. I_DdandI_Dpof these 900 MOSFET pixels are sampled from thes nine uniformly distributed regions across the array. The results demonstrate the uniform photo and dark current distribution. At V_G = 10 V, the average I_Dd in the linear region of V_D= 2V is 41.5 nA, while the average I_Dp is 13.6 μA, yielding a photo-to-dark current ratio (PDCR) of approximately 3.28×10². In the saturation region of V_D= 10V, the average I_Dd is 123.7 nA and the average I_Dp is 46 μA, corresponding to a PDCR of about 3.73×10². The device characteristics are uniform across the entire array. In the saturation region, the responsivity (R), specific detectivity (D*), and external quantum efficiency (EQE) of the device are 849.6 A/W, 1.82×10¹³ Jones, and 4.15×10⁵%, respectively. Ultraviolet projection imaging tests using a hollow-letter mask show that the array can clearly reproduce the pattern of the ‘XUPT’ letters, indicating good uniformity and excellent solar-blind UV imaging capability.
This work demonstrates a 128×128 β-Ga₂O₃ MOSFET solar-blind UV detector array fabricated through collaborative process optimization, achieving large-area integration with high responsivity and large photocurrent. However, the device exhibits a relatively long response time under current fabrication conditions, limiting its applicability to static or low-frequency imaging. Ongoing optimization efforts target three key parameters of material crystallinity, process uniformity, and device structure to systematically reduce the response time. This work should be helpful for the development of large-scale, high-pixel-count Ga₂O₃ MOSFET image sensors.