Hysteresis Behavior and Photoresponse Enhancement in Au Nanoparticle-Decorated Ge Photodetectors

Abstract

Au nanoparticles (NPs) were drop-casted onto germanium (Ge) devices to investigate the influence of Au NPs on the electronic transport and photodetection properties of Ge metal-semiconductor-metal photodetectors. A significant hysteresis behavior was observed in the current-voltage curves of the Au NP-decorated Ge photodetector, which was ascribed to the energy band bending below the Au NPs and the electrostatic effect of image charges in the Au NPs. More interestingly, at the optical communication wavelength of 1.55 µm, the introduction of Au NPs effectively improved the responsivity of the device from 0.18 to 0.92 A/W. Rather than the localized surface plasmon resonance effect, the increase of responsivity in the Au NP-decorated Ge photodetector was caused by a type-II liked energy band alignment, which enhanced the spatial electron-hole separation effect. These results provide inspiration for the development of novel optoelectronic devices. Index Terms-Au nanoparticles (NPs), electric hysteresis loop, electrostatic effect, germanium (Ge) photodetector, photoresponse enhancement. I. INTRODUCTIONG ERMANIUM (Ge) is one of the most promising materials for near-infrared detection [1], [2], owing to the small bandgap (0.67 eV) and the better compatibility with Si-CMOS processes as compared with III−V and II-VI semiconductor materials. However, the low absorption coefficient of Ge material near 1.55 μm, which is attributed to the direct bandgap of 0.8 eV, is still a major obstacle for its application in optical communication [3], [4].

Photothermal‐Induced Electrical Behavior of Micron‐Sized Platinum Structures and Their Efficient Photodetection

“…Therefore, in this Au-NRs/Pt MWs system, the series Pt MWs can collect more thermal changes, and the Au NRs can make the Pt PTE detector more sensitive to photons, both of which contribute to the high photoresponsivity and fast response time of the Au NRs/Pt PTE detector. Compared to other types of metallic nanoparticle based photodetection systems, [48][49][50][51][52][53][54] such as Au NPs/Graphene, [48] Ag NPs/ZnO NWs, [49] Pt NPs/MoS 2 NPs, [50] Al NPs/ZnO NRs. [51] This Au NRs/Pt MWs system achieves a tens of thousands of times improvement in response time, making it competitive with traditional photodetection systems.…”