[Invited Paper] High Sensitivity Crystalline Selenium-based CMOS Image Sensor Using Avalanche Multiplication

Formation of Micro‐Patterned Ga2O3/Se Heterojunction and its Application to Highly Sensitive Avalanche Photodiode

“…Because the re‐evaporation, pinholes, and peeling off from the beneath layer were caused by increasing residual stress during the thermal crystallization of Se thin films, a thin Te layer (<1 nm) was inserted below the Se layer to increase the adhesion of Se to the window layers. [ 3,4,6,7,14,15,32 ] 5) Thermal evaporation of the MoO 3 hole transfer layer (HTL) and Au bottom electrode: 6) Patterning of the Au electrode: Au electrodes were patterned with an iodine‐based etchant. 7) Plasma etching of Se and MoO 3 layers: MoO 3 and Se layers were etched through Au patterns as etching masks using O 2 plasma etching at a flow rate of 30 sccm for O 2 and radio frequency (RF) power of 300 W for 3 min.…”

“…Because the re-evaporation, pinholes, and peeling off from the beneath layer were caused by increasing residual stress during the thermal crystallization of Se thin films, a thin Te layer (<1 nm) was inserted below the Se layer to increase the adhesion of Se to the window layers. [3,4,6,7,14,15,32] 4 and Table 1 show the photographs of the fabricated Ga 2 O 3 /Se micro-PD and the thickness of each layer, respectively.…”

“…[14] A Ga 2 O 3 wide bandgap n-type layer and NiO layer were used as a hole-blocking layer and electron-blocking layer in a Ga 2 O 3 /Se/NiO heterojunction, respectively. [15] Because Ga 2 O 3 has attractive features for applications in n-type window layers of APD such as widegap and direct transition bandgap, it has been applied to thin-film-based solar-blind APD by combining with GaN or SiC. [16,17] Zhao also reported ZnO/Ga 2 O 3 heterojunction which can induce avalanche breakdown efficiently because of a much larger valence band offset than its conduction band offset between ZnO and Ga 2 O 3 layers.…”