Engineering of Ga2O3 based high-performance deep ultraviolet photodetectors using facile growth techniques (PhD)

Abstract

In the present pandemic scenario, people are using ultra-violet (UV) lamps extensively for disinfection purposes at various places such as homes, hospitals, medical diagnosis labs, etc. Any un-intentional exposure to this UV light can be very harmful to the human body if it exceeds certain limits. The use of photodetectors is one of the ways to control the exposer limits of dangerous UV emission. The modernization of the defense sector is another area where these optoelectronics devices find their wide applications such as detecting missile plumes against the glaring background of daylight, infrared (IR) clutter, and more. UV imaging is also having critical importance for UV astronomy. Wide bandgap semiconducting materials with a relatively larger bandgap (>3.23 eV) are suitable for deep UV spectrum sensing. Several semiconducting materials with wide bandgap such as AlGaN, GaN, and ZnO have been proven to be suitable candidates for deep UV sensing. However, these materials require alloying and have various associated defects degrading the detector performance along with expensive fabrication technique. Despite the recent progress in other conducting transparent semiconducting oxides, -Ga2O3 is a perfect candidate of deep UV photodetection with a direct and indirect bandgap of 4.9 eV and 4.85 eV, respectively along with excellent chemical, mechanical and thermal stability. In this context, an inexpensive and scalable electrospinning technique has been opted for the synthesis of various -Ga2O3-nanostructures (NSs) or nanomaterials to fabricate deep UV photodetectors (PDs). We have developed -Ga2O3 nanoflakes (NFs) based deep UV photodetector with impressive photocurrent (Iph) (-9.12×10ð€€€4 A), and dark current (Idark) (4.13×10ð€€€8 A) along with very good responsivity (1.4×103AWð€€€1) at 10 V. Moreover, the Ga2O3 has been alloyed with Indium (In) to increase the free carriers in the channel for enhancement of the optoelectronic properties of the PDs. The GaInO3 nano-wires (NWs) based deep UV photodetector has shown remarkable responsivity (>1.2×104 AWð€€€1) with a comparatively high Idark (2.81×10ð€€€7 A) at 1 V bias. However, the high dark current makes the devices a power-hungry unit even at standby operation. Therefore, to reduce the dark current, a novel technique has been employed involving quasi-heterostructure of n-Ga2O3/p-CuO based metal-semiconductormetal (MSM) UV photodetector which reduced the Idark (6.94×10ð€€€14 A) significantly with extremely high responsivity (>6.0×103 AWð€€€1) at 5 V. However, the responsivity and Iph (2.08×10ð€€€7 A) have decreased in comparison to the earlier works. Hence, Ga- In nanoparticles have been used with the potential plasmonic effect to further improve the photocurrent of the photodetectors. After the incorporation of the nanoparticles on top of the previous heterostructure devices, photo to dark current ratio (PDCR), and Iph (1.14×10ð€€€5 A) have been enhanced significantly along with a very low dark current (1.03×10ð€€€13 A) at 5 V. Thus, all the fabricated devices have exhibited a very high photo to- dark current ratio (PDCR), responsivity, detectivity, and external quantum efficiency as compared to the earlier state-of-the-arts leading to a significant impact on upcoming UV detector technology.