Silicon-Based Grid Structure Photodiode with Selective UV Enhancement

Aiming at boosting the low ultraviolet (UV)re-sponsivity induced by thenegative impact of the surface 'dead layer' in silicon-based conventional photodiode (CPD), Siphotodiodes with five different structures, including both the novel grid structurephotodiode(GSPD)and CPD, have been manufactured using thermal diffusion process and tested. The results show thatthe UV responsivity around 365 nm of GSPD could be as high as 6 times that of CPD, while the highvisible (VIS) responsivity is sharply suppressed by the employment of grid shaped junction (GSJ) inthe GSPD, which has realized the expectation of selective UV enhancement with prospect forapplication.

Design, Fabrication, and Measurement of Two Silicon-Based Ultraviolet and Blue-Extended Photodiodes

Two silicon-based ultraviolet （UV） and blue-extended photodiodes are presented, which were fabricated for light detection in the ultraviolet/blue spectral range. Stripe-shaped and octagon-ring-shaped structures were designed to verify parameters of the UV-responsivity, UV-selectivity, breakdown voltage, and response time. The ultra-shallow lateral pn junction had been successfully realized in a standard 0.5-μm complementary metal oxide semiconductor （CMOS） process to enlarge the pn junction area, enhance the absorption of UV light, and improve the responsivity and quantum efficiency. The test results illustrated that the stripe-shaped structure has the lower breakdown voltage, higher UV-responsicity, and higher UV-selectivity. But the octagon-ring-shaped structure has the lower dark current. The response time of both structures was almost the same.

Polarization-induced photocurrent switching effect in heterojunction photodiodes

The unipolar photocurrent in conventional photodiodes(PDs)based on photovoltaic effect limits the output modes and potential versatility of these devices in photodetection.Bipolar photodiodes with photocurrent switching are emerging as a promising solution for obtaining photoelectric devices with unique and attractive functions,such as optical logic operation.Here,we design an all-solid-state chip-scale ultraviolet(UV)PD based on a hybrid GaN heterojunction with engineered bipolar polarized electric field.By introducing the polarization-induced photocurrent switching effect,the photocurrent direction can be switched in response to the wavelength of incident light at 0 V bias.In particular,the photocurrent direction exhibits negative when the irradiation wavelength is less than 315 nm,but positive when the wavelength is longer than 315 nm.The device shows a responsivity of up to−6.7 mA/W at 300 nm and 5.3 mA/W at 340 nm,respectively.In particular,three special logic gates in response to different dual UV light inputs are demonstrated via a single bipolar PD,which may be beneficial for future multifunctional UV photonic integrated devices and systems.