Advanced Semiconductor Materials and Devices Group

Ultra-Wide band Gap (UWBG) Solar-Blind Photodetectors

Modern day technologies are seeing a huge thrust in the development of smart materials and devices. These materials and devices have qualities such as lightweight, transparency, robustness, flexibility, environmentally friendliness, and lowcost and enrich human life with advanced functionalities. Besides the smart functionalities, various flexible sensors can be useful for healthcare as well.

The ultrahigh photoresponsivity of 9.7 A/W is obtained for 5 V applied bias at room temperature under 75 μW/cm2weakillumination of 270 nm wavelength. The detector enables very low noise equivalent power (NEP) of 9×10⁻¹³ W/Hz^1/2 and ultrahigh detectivity of 2×10¹² jones which shows the magnificent detection sensitivity. Further, bending tests are performed for robust utilization of flexible detectors up to 500bending cycles with each bending radius of 5 mm. After 500 bending cycles, the device shows a slight photocurrent decrease. The bending performances exhibit excellent potential for wearable applications. Moreover, photocurrent and dark current characteristics above room temperature demonstrate the outstanding functionalities until 523 K temperature, which is remarkable for flexible photodetectors. The obtained results show the potential of gallium oxide solar-blind photodetectors at room-temperature and high-temperature environments, paving the way for futuristic smart sensors.

Deep Ultraviolet Detector on mica substrate (Ram et. al 2019)

Deep ultraviolet photodetectors (DUVPDs) (<280nm), also known as solar-blind PDs, have piqued interest due to their wide range of applications in defence, space communication, civil, agriculture, healthcare, UV astronomy, high-temperature flame detection, solar-blind imaging for missile tracking, ozone hole monitoring, and other fields. Wide-bandgap and ultrawide-band-gap semiconductor materials such as GaN, AlGaN, diamond, Lu2O3, and Ga2O3have emerged as promising candidates for solar-blind PDs because of their wide- and ultrawideband gap due to which they exhibit intrinsic solar-blindness. Unlike commercially available UVPDs based on narrow-band-gap semiconductor materials such as Si and GaAs, they do not require any additional optical filter or large cooling systems.

Here in our work, we have grown thick gallium oxide incorporated with buffer layer of gallium oxide to maintain high quality of crystallinity on the sapphire by the MOCVD, the fabricated the device through the lithography followed by metallization. The performance of device in summarized way ultra-high-performance DUV PDs based on UID MOCVD-grown β-Ga2O3were fabricated, and the gain and the self-powered behavior were thoroughly investigated. The high-temperature stability of DUV PDs on films up to 125°C was demonstrated. The dark current was observed to be extremely low and found to be almost constant across the whole temperature range. The UV−visible (260:500nm) rejection ratio was found to be >10³ at zero bias and >10⁵ at higher biases, and it increased with the rise of temperature. All other performance parameters of PDs remained at high values throughout the entire temperature range. The Schottky barrier height lowering effect caused by an induced electric field and localized self-trapped holes at Ni/β-Ga2O3interfacewere attributed to the gain mechanism. The self-powered behavior of PDs was attributed to the barrier inhomogeneity at the Ni/β-Ga2O3interface.

Schematic of the Ga₂O₃ Device (Hardhyan et. al. 2022)

The Dynamic temporal temperature-based performance. (Taslim et.al.)

The use of 2D materials as potential substitutes for conventional 3D electrical connections has grown considerably in recent years. These materials have special benefits, when used to create van der Waals (vdW) heterojunctions. These heterojunctions are not obligated to conform to the strict requirements for lattice matching and processing compatibility that are present in conventional bonded heterojunctions, and there is no chemical reaction taking place at the interface, as opposed to while metal contacts with semiconductors react to produce oxide and nitrides. Traditionally only metal and oxide electrode have been utilized in in device fabrication Ag, Graphite, Ni/Au, Pt/Au, Cr/Au, Ti/Au, ITO, IZO and IGZO.