Fabrication of PureGaB Ge-on-Si photodiodes for well-controlled 100-pA-level dark currents

A. Sammak*, M. Aminian, L. Qi, W. B. De Boer, E. Charbon, L. K. Nanver

*Corresponding author for this work

Research output: Contribution to journalConference articleAcademicpeer-review

3 Citations (Scopus)

Abstract

The selective epitaxial growth of Ge-on-Si followed by in-situ deposition of a nm-thin Ga/B layer stack (PureGaB) has previously been shown to be a robust CMOS-compatible process for fabrication of Ge-on-Si photodiodes. In this paper, strategies to improve the control and reproducibility of PureGaB Ge-on-Si photodiode fabrication by reducing the local loading effects during the depositions are presented. As compared to the earlier PureGaB devices, the elimination of parasitic Ge and concomitant in-situ As-doping from oxide regions surrounding the deposition windows leads to a well-controlled process flow that improves photodiode electrical and optical characteristics. For micrometer-sized diodes, ideality factors of less than 1.1 and dark current densities in the range of 15 μA/cm2 at room temperature are now achieved. Moreover, improvements in the flatness of the Ge-island surface facilitated a process flow for contacting the diode perimeter while leaving a large oxide-covered PureGaB-only light-entrance window on the central photosensitive region. The optical characteristics of the photodiodes at the low temperature of 180 K display dark current densities of less than 150 pA/cm2 and increased sensitivity towards infrared wavelengths.

Original languageEnglish
Pages (from-to)737-745
Number of pages9
JournalECS transactions
Volume64
Issue number6
DOIs
Publication statusPublished - 1 Jan 2014
Externally publishedYes
Event6th SiGe, Ge, and Related Compounds: Materials, Processing and Devices Symposium - 2014 ECS and SMEQ Joint International Meeting - Cancun, Mexico
Duration: 5 Oct 20149 Oct 2014

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