TITLE:
Development of Low Dark Current SiGe Near-Infrared PIN Photodetectors on 300 mm Silicon Wafers
AUTHORS:
Caitlin Rouse, John W. Zeller, Harry Efstathiadis, Pradeep Haldar, Jay S. Lewis, Nibir K. Dhar, Priyalal Wijewarnasuriya, Yash R. Puri, Ashok K. Sood
KEYWORDS:
Photodetectors, Infrared Detectors, Germanium, Photodiodes, Large-Area Wafers
JOURNAL NAME:
Optics and Photonics Journal,
Vol.6 No.5,
May
16,
2016
ABSTRACT: SiGe offers a
low-cost alternative to conventional infrared sensor material systems such as
InGaAs, InSb, and HgCdTe for developing near-infrared (NIR) photodetector
devices that do not require cooling and can operate with relatively low dark
current. As a result of the significant difference in thermal expansion
coefficients between germanium (Ge) and silicon (Si), tensile strain incorporated
into SiGe detector devices through specialized growth processes can extend
their NIR wavelength range of operation. We have utilized high throughput,
large-area complementary metal-oxide semiconductor (CMOS) technology to
fabricate Ge based p-i-n (PIN)
detector devices on 300 mm Si wafers. The two-step device fabrication process,
designed to effectively reduce the density of defects and dislocations arising
during deposition that form recombination centers which can result in higher
dark current, involves low temperature epitaxial deposition of Ge to form a
thin p+ seed layer,
followed by higher temperature deposition of a thicker Ge intrinsic layer. Phosphorus
was then ion-implanted to create devices with n+ regions of various doping concentrations. Secondary
ion mass spectroscopy (SIMS) has been utilized to determine the doping profiles
and material compositions of the layers. In addition, electrical
characterization of the I-V photoresponse of different devices from the same
wafer with various n+ region doping concentrations has demonstrated low dark current levels (down to
below 1 nA at -1 V bias) and comparatively high photocurrent at reverse biases,
with optimal response for doping concentration of 5 × 1019 cm-3.