Mid-Infrared Single Photon Counting Photodetectors for Quantum Biosensing
Authors:
Leon Shterengas* ([email protected], PI), Egor Portyankin, Gela Kipshidze, Jinze Zhao, Dmitri Donetski
Institutions:
State University of New York at Stony Brook
Goals
The overall project goal is to develop single photon counting avalanche photodiodes (SPAD) operating in mid-infrared spectral range above 3 micrometers. Application of the novel devices as a bucket detector in mid-infrared quantum ghost imaging of biological tissue is envisioned.
Abstract
The team designed and fabricated GaSb-based separate absorption, charge, multiplication (SACM) heterostructures optimized for hole- initiated impact ionization. The devices were grown onto tellurium- doped GaSb substrates and contained 1 µm– thick nominally undoped InAs0.91Sb0.09 absorber, ~100 nm–thick tellurium-doped Al0.9Ga0.1As0.07Sb0.93 and 300 nm–thick nominally undoped Al0.9Ga0.1As0.07Sb0.93 multiplier layer terminated with ~300 nm–thick phosphorous-doped contact layers. The epitaxial wafers were processed into 40 and 80 diameter shallow etched mesa devices with, correspondingly, 20 and 60 µm diameter windows in top contact metallization. The SACM APD were indium-soldered epi-side-up with onto gold-plated carriers and characterized in wide temperature range.
The punch-through voltage was about 10 volts at liquid nitrogen temperature; dark and photocurrent current increase due to avalanche breakdown was observed at voltages above 13 V, which was taken as a unity gain voltage reference. The linear regime multiplication gains exceeding 200 were observed at voltages near 17.5 V at liquid nitrogen temperature. The dark current values of several nanoamperes have been recorded for all devices before the breakdown. The analysis of the temperature dependence of the dark current above punch-through confirms diffusion limited absorber operation at temperatures above 150°K (activation energy ~370 megaelectron volts). At temperatures below ~150°K, the dark current became ~nA and its dependence on temperature was characterized by activation energy ~10 millivolts indicating other current controlling mechanisms.
The dark current values below punch-through voltage at temperatures below 200°K remained under 100 picoamperes and were virtually temperature independent for all devices. Independently characterized responsivities values above 5 amperes per watt at bias voltages corresponding to linear gain values below 10. The device cutoff wavelength at liquid nitrogen temperature was ~3.9 µm as determined at the half maximum level. Experiment confirmed efficiency of the proposed device architecture, which does not require etching through absorber section. The observed mismatch of about several volts between punch through and start of the avalanche breakdown indicates that thickness of the multiplier section and doping level of the charge control section will need to be optimized to further reduce dark current values.
Funding Information
This research was supported by the DOE Office of Science, BER program, grant DE-SC0023165.