1. National Institute Of Standards and Technology
Boulder Colorado
Enhancing the Performance of Quantum-Dot Based Single-Photon Detectors
using Resonant RLC Circuitry
Dean’s Distinguished Fellowship – Summer 2013
QDOGFET detectors use QDs embedded
in transistors to count single photons of
light.
Previous work has been done at low
detection rates and low operating
temperatures.
For practical application, high operating
temperatures and detection rates are
desired.
Here, we discuss the technique of
integrating the QDOGFET detector into
an RLC Bandpass Filter to remove
unwanted electrical noise from our
signal
Intro QDOGFET Design and Concept
-2 -1 0
0
20
40
60
80
DVgate
DIds
N=3
Vgate (V)
Ids(mA)
• Ni/Au/Ge Source and Drain
Ohmic Contacts
SEM Image
• QD Density: 400-500 QDs/mm2
• Semitransparent Pt Gate
2DEG
CB
VB
InGaAs QDs Si d-doping
GaAs
Al0.2Ga0.8As
Source
Al0.2Ga0.8As
Drain
Gate
GaAs
QDOGFET Noise
Vout(a.u.)
Time (ms)
Electrical Noise
The main problem when analyzing our
signal is the electrical noise.
When we look at the noise in the
frequency domain, we observe a fine
structure. Our studies have shown that
noise is of the form:
10
2
10
3
10
4
10
5
10
-26
10
-25
10
-24
10
-23
10
-22
10
-21
10
-20
10
-19
7K
11K
18K
30K
43K
60K
10 20 30 40 50 60
0
1
2
NI(A2/Hz)
B(A)
Frequency (kHz)
Temperature (K)
The noise increases with
temperature.
Filtering the Noise with a Band Pass Filter
We can minimize the noise by using a RLC Band Pass Filter, using our QDOGFET
as the resistive element.
Capacitor
Inductor
VBP
Vout
RQ
Vgate
18 20 22 24 26 28
0
10
20
30
40
50
60
70
Frequency (kHz)
Conclusions and Future Work
Understanding the noise features and their temperature dependence is
critical in identifying the sources of noise
Identifying the noise mechanisms is necessary for:
 Engineering better performing devices
 Determining maximum detection rates
Determine operating temperature limitations
Still to come:
 Increased detection efficiency
 Improved photon-number resolution
 Modified structures for communications wavelengths (1310 and 1550 nm)
What we achieved:
QD Detector
Photon-Number Resolution at 4K
Laser
l = 804 nm
LHe Cryostat
4 K
Attenuating
Filter
N=2 N=0 N=1 N=0 N=2 N=1
E. J. Gansen et al., Nature Photonics 1, 585 (2007).
We use Poisson statistics of highly attenuated laser pulses to
show photon counting capabilities.
0.0 0.4 0.8
0.0
0.4
N = 1
Histogram of Step Heights
N=0
N=1
N=2
N=3
DIds (nA)
Data
Fit
0 250 500
16.246
16.247
16.248
16.249
Time (ms)
ResetLaser
DIds
Ids(mA)
With the new filtering technique the device should be able to reach
signal to noise ratios of over 20:1.
Signal to Noise with the filter
Counts(x1000)
Response to Single Pulse
25
20
15
10
5
0 50 100 150 200 250 300
3:1 S/N Line
Temperature (k)
•23:1 at 4k (Liquid
Helium)
•7:1 at 77k (Liquid
Nitrogen)
•3:1 at 222k
(Thermoelectric
Cooling)
•2.3:1 at 296k (Room
Temperature)
Filtered Photo-Response at 6K
Histogram of Step Heights
Laser Pulse
ΔVout
Response to Single Pulse
We looked at the amplitude of Vout while illuminating the device
with 804 nm laser.
Each photon changes the resistivity of
the QDOGFET, which changes the
resonant conditions of the RLC circuit.
As a result, it causes measurable
changes in the amplitude of Vout .
We can analyze the
changes in |Vout |by
using our histogram.
A mathematical fit
helps us determine
regions of detection
of photons (N=0,
N=1 etc…).
-1.5 -1.0 -0.5 0.0
50
55
60
65
DVgate
DVout
N=1
|Vout|(mV)
|Vgate|(V)
15000 15500 16000 16500 17000
0.0
0.2
0.4
0.6
0.8
1.0
3 photons
2 photons
1 photon
0 photon
We simulated the behavior of the
amplitude of Vout as a function of
frequency.
Experiment Experiment
Simulation
Frequency (kHz)
|Vout| (mV)
fresonant
-0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10
0
200
400
600
Counts |DVout|(V)
Data
Fit
N=0 N=1 N=2 N=3
In a second time, we experimentally
characterized the RLC circuit at 6K.
|Vout|(mV)
S/N
Photons of light cause
measurable changes in
the amplitude of Vout. We
average |Vout | before
and after the pulse of
light in order to build a
histogram
UW-L : Yann Talhouarne, Andrew Prudhom, Tyler Nickel, Richard Allenby, Eric Gansen (Advisor)
NIST : Mary Rowe, Shelley Etzel, Sae Woo Nam, and Richard Mirin