IIT Jodhpur
Webinar Series "Deep Diving into Physics" by Prof Mukesh Kumar titled "Solar-Blind Photodetectors: Charge dynamics, flexibility, and stability" on 22 September 2021

The fourth speaker of the webinar series Deep Diving into Physics, Prof Mukesh Kumar from Department of Physics, IIT Ropar introduced the working of solar photodetectors to our students.


Solar-blind photodetectors are an emerging technology for forest fires, territory intrusions, ozone hole monitoring, deep space exploration, satellites, and secure communication. A photodetector working in the <280 nm, solar-blind region, could minimize the chances of false radiation detection even under intense sun interference on the earth’s surface by detecting ozone layer filtered deep UV (UV-C) terrestrial signatures. Here, we demonstrated an ultrahigh-performance and self-powered β-Ga2O3 thin film solar-blind photodetector fabricated on a cost-effective Si substrate using a high-temperature seed layer (HSL). The zero-bias digitizing sensor prototype with an HSL produces a digitized output bit with deep UV (DUV) light that exhibits a high on/off (I254 nm/Idark) ratio of >103, a record-low dark current of 1.43 pA, and high stability and reproducibility over 100 cycles even after >4000 h. However, developed traditional photodetectors showed a unipolar photocurrent response when illuminated with light of wavelength equal or shorter than the optical bandgap. Surprisingly, the Ag nanoparticle decorated β-Ga2O3 photodetector exhibits a change in the polarity of the photocurrent for different UV bands. The photodetector shows a record responsivity of 250 A W−1, which significantly outperforms bare GO planar photodetectors along with opposite response with UVA and UVC bands. The current reversal is rationalized by considering the charge dynamics stemming from hot electrons generated when the incident light excites a local surface plasmon resonance in the Ag nanoparticles. Paper based super-flexible, non-wettable, self-powered and high-voltage stable amorphous gallium-oxide photodetector is also fabricated and investigated in details.

The gallium oxide thin films and grown photodetector is also investigated against extreme environment conditions for their space applications. We have studied the radiation hardness and device performance of amorphous and polycrystalline gallium oxide thin films against swift heavy ion (Ag7+) irradiation with a high energy of 100 MeV. The effect of self-annealing at room temperature and annealing at moderate temperature is investigated to recover the irradiated photodetector devices. Partial recovery in the polycrystalline based photodetector and two orders of magnitude enhanced responsivity and an almost twice faster response time compared to the control photodetectors in the amorphous phase are observed. Our research activities provide the guidelines to develop a β-Ga2O3-based cost-effective, self-powered, high-performance, and fast DUV photodetector that possesses a high potential for next-generation practical solar-blind photodetector application.