High-Performance Lateral Metal-Germanium-Metal SWIR Photodetectors Using a-Si:H Interlayer for Dark Current Reduction

Abstract

In this work, we propose the lateral metal-germanium-metal photodetectors (PDs) structure on the silicon-oninsulator platform for short-wave infrared (SWIR) applications. The proposed device utilizes the highly n-doped amorphous silicon (a-Si:H) interlayer between metallic contact and low n-doped germanium active region to achieve a low dark current. Additionally, the tuning of Schottky barrier height (SBH) by the selection of various metallic contacts (Cr/W/Mo) has been investigated in order to achieve a large reduction in dark current. With a-Si:H interlayer and Mo metallic contacts at both anode and cathode terminals, the simulated energy band diagram shows that an effective increase in SBH of 0.17 eV and 0.766 eV for electrons and holes, respectively, and thus acts as barriers for electron and hole dark currents. The result shows that the Mo metallic contact device manifests the least dark current (dark current density) of 0.27 pA (0.027 mA/cm 2 ) at V bias of 0.25 V and compared to Cr contact, it has been significantly decreased by two orders of magnitude. In addition, with Mo contact, the proposed device achieves the photogenerated-to-dark current (I ph /I dark ) ratio and the responsivity of ∼ 1.7 × 10 6 and 0.96 A/W, respectively at λ = 1.55 µm with V bias of 0.25 V. Furthermore, the proposed Mo-Ge-Mo PD shows high detectivity (NEP) of 9 × 10 11 cmHz 1/2 W −1 (∼ 3 × 10 −16 WHz −0.5 ), which is nearly 15 (one order lower) times higher than those of Cr-Ge-Cr PD. The results hold great potential for optoelectronic applications requiring low-power Ge-based PD.

Hot-Carrier Effect and Nanometer Metal Enabling Si-Based Mid-Infrared Detection Beyond 5μm of Wavelength

“…Fields such as atomic physics [1], astronomy [2], and medicine [3][4][5] rely heavily on broadband optical detection, particularly in the mid-infrared range. The past works have focused on mid-infrared photonic integrated circuit sensing platforms based on material such as narrow-gap semiconductors (InGaAs [6][7][8][9], InAs [10], InSb [11], Ge [12],…”