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

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

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

Electrical Engineering, Mathematics and Computer Science

Microelectronics

2014-06-01

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.

http://resolver.tudelft.nl/uuid:db7f8124-5f80-4b09-a282-64064b468f20

https://doi.org/10.1149/06406.0737ecst

Electrochemical Society

1938-5862

ECS Transactions, 64 (6), 2014

Institutional Repository

journal article

© 2014 The Electrochemical Society