Two-Step Liquid Phase Crystallized Germanium-Based Photodetector for Near-Infrared Applications

Kumar, S and Chatterjee, A and Selvaraja, SK and Avasthi, S (2020) Two-Step Liquid Phase Crystallized Germanium-Based Photodetector for Near-Infrared Applications. In: IEEE Sensors Journal, 20 (9). pp. 4660-4666.

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Abstract

This work presents a wafer-scale two-step liquid phase crystallization process to obtain polycrystalline but epitaxial germanium on 2'-silicon wafers (Ge-on-Si). The crystallinity is confirmed using Raman spectroscopy and X-ray diffraction, with an extracted dislocation density of 108cm-2, an improvement of 10x over the previous report. The scanning electron imaging shows a uniform Ge film with a grain size of up to 12� m. Metal-semiconductor-metal (MSM) near-infrared (IR) photodiodes are fabricated on the epitaxial Ge with two different electrodes and two different surface passivation interlayers. Irrespective of the electrode/passivation combination, all devices exhibit Ohmic characteristics. Contact resistivity varies from 3 mΩ cm2 to 560 mΩ cm2. This is contrary to virtually every previous report on MSM detector on n-type Ge. To probe further, kelvin probe force microscopy is used to characterize the surface potentials at grain boundaries and metal-Ge interfaces. The grain-to-grain band bending is very low, 40 meV, hence, device characteristics are completely dominated by the metal-Ge band-bending which is 150-300 meV. The MSM devices using amorphous-Ge(30nm)/Al(100nm) and TiO2 (5nm)/Au(80nm) electrodes show an average spectral responsivity (SR) of 0.50 ± 0.16 A/W and 0.35 ± 0.09 A/W at 1550 nm and voltage bias of -3V, respectively. The maximum SR is 0.78 A/W and 0.48 A/W, respectively. © 2001-2012 IEEE.

Item Type:	Journal Article
Publication:	IEEE Sensors Journal
Publisher:	Institute of Electrical and Electronics Engineers Inc.
Additional Information:	Copyright for this article belongs to IEEE
Keywords:	Aluminum compounds; Crystallinity; Electrodes; Germanium compounds; Gold compounds; Grain boundaries; Metals; Passivation; Silicon wafers; Titanium dioxide, Contact resistivities; Device characteristics; Dislocation densities; Kelvin probe force microscopy; Metal semiconductor metal; Near-infrared applications; Ohmic characteristics; Spectral responsivity, Infrared devices
Department/Centre:	Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering
Date Deposited:	02 Sep 2020 10:12
Last Modified:	02 Sep 2020 10:12
URI:	http://eprints.iisc.ac.in/id/eprint/65157

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