In the near-infrared range,numerous applications have extensive demands for Single-photon Detection,including fluorescence lifetime imaging(FLIM)[
Journal of Infrared and Millimeter Waves, Volume. 43, Issue 1, 1(2024)
High detection efficiency InGaAsP/InP single-photon avalanche diode at room temperature
We described a high-performance planar InGaAsP/InP single-photon avalanche diode (SPAD) with a separate absorption, grading, charge and multiplication (SAGCM) heterostructure. By electric field regulation and defects control, the SPAD operated in the gated-mode at 293 K with a photon detection efficiency (PDE) of 70%, a dark count rate (DCR) of 14.93 kHz and an after-pulse probability (APP) of 0.89%. Furthermore, when operated in the active quenching mode with a dead time of 200 ns, a PDE of 12.49% and a DCR of 72.29 kHz were achieved at room temperature.
Introduction
In the near-infrared range,numerous applications have extensive demands for Single-photon Detection,including fluorescence lifetime imaging(FLIM)[
Currently,the performance of InGaAs(P)/InP SPADs has been greatly improved. One study[
In this paper,a planar front-illuminated InGaAsP/InP SPAD made of a SAGCM structure was fabricated. On the one hand,the deep-level defects of the SPAD were reduced by adjusting the diffusion conditions. On the other hand,a high avalanche probability was guaranteed by improving the design of electric field distribution. Both of these factors contributed to the realization of single-photon detection at 293 K,with a PDE of 70% and a DCR of 14.93 kHz,which is the highest level achieved in InGaAsP/InP SPADs operating at room temperature so far.
1 Structure and fabrication
As shown in
Figure 1.Cross-sectional schematic of the InGaAsP/InP APD
Here,the Sentaurus-TCAD,a commercial software,was used to simulate the performance of InGaAsP/InP SPAD. A 2D electric field distribution at a bias voltage of 2 V is shown in
Figure 2.2D electric field distribution at 2 V over bias
For a SPAD,the PDE can be expressed as the product of three probabilities,as shown in the
Here,
Figure 3.Calculated
2 Results and Discussions
The sample and a three-stage thermoelectric cooler(TEC)were integrated together inside a To-66 tube shell,as shown in
Figure 4.Physical appearance of an InGaAsP/InP SPAD
Figure 5.I-V curves at different temperatures
A gated-mode single-photon detection system,as shown in
Figure 6.Schematic diagram of gated-mode single-photon detection system
At an operating temperature of 293 K,the PDE was varied by adjusting the bias voltage of the SPAD. The corresponding DCRs and after-pulse probabilities(APPs)for different PDEs were measured,and then,it is presented in
Figure 7.DCRs and APPs corresponding to different PDEs at 293 K
DCR refers to the count when there was no photons incident,mainly derived from the thermal noise and tunneling noise of the device. This parameter can be calculated using
The SPAD not only exhibited excellent performance at room temperature but also performed well at low temperatures. As shown in
Figure 8.The DCR versus temperature at different PDEs
In order to further analyze the origin of the DCR,the activation energy(Ea)was extracted,which can quantitatively describe the composition of the device’s dark current. As shown in
Figure 9.Linear fit of
Figure 10.Ea versus PDEs
An InGaAsP/InP SPAD operated in Geiger-mode with a high reverse bias voltage has a dark current consisting of several components,including the generation-recombination(G-R)current
Where
Here,the G-R current has a strong temperature dependence,including the Shockley-Read-Hall(SRH)dark current associated with deep-level defects and the valence to conduction G-R current. The tunneling current comprises of both BTB and TAT currents,which correlate with the temperature weakly and are in direct proportion to the square of the electric field. The former is due to direct tunneling from the valance band to the conduction band,influenced by relatively high reverse bias voltage in narrow band gap semiconductors and can be reduced by adjusting the thickness of the multiplication layer. The latter originates from the tunneling of electrons via trap levels to the conduction band,influenced by defects in the device. Thus,Ea has been maintained at fixed value,indicating that:(1)As the PDE increases,the tunneling current should rapidly increase with the electric field,resulting a decrease of Ea. However,in this case,Ea remained almost unchanged,indicating that the tunneling current is very small compared to the G-R current,suggesting that there are few defects in the multiplication region.(2)The G-R current accounts for a larger proportion in the dark current. Considering that a portion of it is induced by the valence to conduction generation current while the other part is limited by the deep-level defects,the fixed activation energy close to half of the bandgap energy of InGaAsP indicates that the deep-level defects induced G-R current is dominant. The G-R current varies little with
When an avalanche occurs,some carriers may be captured by the defects in the material. When the next gate pulse arrives,these captured carriers can cause new avalanches,leading to false signals known as the after-pulse effect. During testing,we set the gate pulse frequency to 1 MHz and the laser frequency to 100 kHz,so for every 10 electrical pulses,only one electrical pulse contains an optical signal. By comparing the counts of the specific electrical pulse containing optical signal and the remaining 9 electrical pulses,the APP was calculated using
Figure 11.APPs versus temperatures at different PDEs
To further characterize the device’s performance,it was also operated in active quenching mode with a dead time of 200 ns,and the results are shown in
Figure 12.PDEs at different temperatures under the active quenching mode
Figure 13.DCRs at different temperatures under the active quenching mode
3 Conclusions
A planar front-illuminated InGaAsP/InP SPAD was presented in this paper. Through electric field regulation,the SPAD’s electric field was mainly concentrated in the center of the multiplication region. Analysis of the activation energy indicated that the main factor affecting the device's DCR was the thermally excited generation-recombination current,and the low number of deep-level defects in the device ensured excellent performance. In gated-mode operation,the InGaAsP/InP SPAD achieved a high PDE of 70% at 293 K,with a low DCR of only 14.93 kHz and an APP of 0.89%. The outstanding performance at room temperature expands the potential applications of the InGaAsP/InP SPADs.
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Yu-Fei QI, Wen-Juan WANG, Jing-Hua SUN, Wen WU, Yan LIANG, Hui-Dan QU, Min ZHOU, Wei LU. High detection efficiency InGaAsP/InP single-photon avalanche diode at room temperature[J]. Journal of Infrared and Millimeter Waves, 2024, 43(1): 1
Category: Research Articles
Received: Mar. 31, 2023
Accepted: --
Published Online: Dec. 26, 2023
The Author Email: WANG Wen-Juan (wangwj@mail.sitp.ac.cn), LU Wei (luwei@mail.sitp.ac.cn)