Infrared detectors that operate in the middle-wavelength infrared (MWIR)range are essential for many applications,such as satellite communications,target tracking,and object identification[
Journal of Infrared and Millimeter Waves, Volume. 42, Issue 3, 306(2023)
Liquid Phase Epitaxy (LPE) growth of the room-temperature InAs-based mid-infrared photodetector
The material quality is very important to obtain the high performance infrared detector. It is presented that the key issue of the material quality is to control the lattice mismatch between the layers of the device architecture. The effects of the lattice mismatch on the material quality and the dark current characteristics were reported. In the InAs/InAsSbP system grown by LPE technology, there is an appropriate value for the lattice mismatch between InAsSbP and InAs. If the lattice mismatch deviates from this value, no matter whether it is smaller or larger, the material quality will deteriorate. Then it was stated how to adjust growth parameters to obtain the appropriate lattice mismatch. The infrared detector made from the device architecture with the appropriate lattice mismatch was fabricated, and the room-temperature peak detectivity of this detector is 6.8×109 cm Hz1/2W-1 at zero bias, which is comparable with that of international commercial InAs photodetectors.
Introduction
Infrared detectors that operate in the middle-wavelength infrared (MWIR)range are essential for many applications,such as satellite communications,target tracking,and object identification[
In Ref. [
1 Experiments
The samples were grown on (100)-oriented InAs substrate by LPE technology,using a conventional horizontal sliding graphite boat. The precursors for the growth melts were undoped polycrystalline InAs,InP,and 7 N pure Indium (In)and Antimony (Sb). InAs substrates were rinsed successively with acetone,isopropanol,and deionized water. They were then etched using a mixture solution (H2O2:HNO3 = 5:3)to remove the native oxide layer on their surface. Prior to the epitaxial growth,the source materials were baked at 650 °C for 2.5 hours under a purified hydrogen gas flow (hydrogen gas purifier:Simpure 9NP050-H)to homogenize and remove the volatile impurities. Growth was initiated at 550 ℃ using the supercooling technique.
The structural properties of the epilayers were investigated by high-resolution X-ray diffraction (HRXRD)measurements (D8/Discover 2 000,Bruker,Germany). Only Cu Kα1 line (λ=1.540 6 Å)was provided through the Ge (220)monochromator. The cross-section micrographs of device samples were observed by scanning electronic microscopy (SEM)(Sirion 200D1615,FEI,USA)measurements. Before the SEM observation,the samples were corroded using the corrosive A-B solution (A:40 cm3 H2O + 0.3g AgNO3+40 cm3 HF and B:40g CrO3+ 40 cm3 H2O)for 3 seconds to display clear interfaces. The resulting structure was processed into 200 μm-diameter mesa-etched photodiodes using conventional photolithography and processing techniques. Ohmic contacts were formed by the thermal evaporation of Cr/Au. No attempts were made to passivate the surfaces. The spectral response was measured using a Nicolet Is50 FTIR spectrometer. The light emitted by a blackbody source passed through the interferometer and was collected by the device. The detectivity D* was measured using a blackbody temperature of 900 K,a testing bandwidth of 100 Hz,and a modulation frequency of 1000 Hz.
2 Results and discussions
2.1 LPE growth of InAsSbP epilayer on InAs substrate
A serial of samples with the different lattice mismatches of 0.4-0.07% were grown by LPE technology.
Figure 1.(a)HRXRD patterns of samples S1-S6 and (b)rocking curves of (400)peaks of InAsSbP epilayer of samples S1-S6
Figure 2.Optical surface morphology of samples S1-S6
2.2 LPE growth of the device material
We have designed the three device samples D1-D3 with different lattice mismatch of 0.09%,0.21% and 0.40%. We intend to study how the detector performance will be when the lattice mismatch deviates from the appropriate value of about 0.2%.
Figure 3.The structure schematic of the device samples D1-D3
In the abovementioned epi-structure,there are three interfaces of InAsSbP barrier/InAs substrate,InAs absorber/InAsSbP barrier,and InAs absorber / InAsSbP window,which involve the lattice mismatch of InAsSbP and InAs.
The HRXRD patterns of the three device samples D1-D3 are shown in
Figure 4.The HRXRD patterns of the device samples D1-D3
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2.3 Device performance analysis
Typical I-V curves obtained at room temperature for the device samples D1-D3 are shown in
Figure 5.I-V curves of device samples D1-D3
where Ri is the device responsivity,Jd is the dark current density,q is the electron charge,Kb is the Boltzamnn constant,T is the temperature,R is the dynamic resistance,and A is the detector area. The peak detectivity was calculated to be 6.8×109 cm Hz1/2W-1,which is nearly 1.5-2.5 times that of the Teledyne Judson Technologies [
Figure 6.The responsivity and detectivity of device sample D2 measured at room temperature
3 Conclusion
The paper reported the LPE growth of the high room-temperature performance mid-infrared InAs-based photodetector. It is proposed that careful control of the lattice mismatch between InAsSbP and InAs is crucial for obtaining the expected performances. In the InAs/InAsSbP system grown by Liquid Phase Epitaxy,it is found that the lattice mismatch between InAsSbP and InAs is not the smaller the better,but there is an appropriate value,which is about 0.20%. When the lattice mismatch deviates from this value,the surface morphology of the material deteriorates,this leads to the increase of the dark current of the detector. The detector architecture with the appropriate lattice mismatch was obtained by adjusting the growth parameters such as the mole fraction of the antimony,phosphorus and arsenic in liquid composition and the growth temperature. Finally,the infrared detector made from the device material with the appropriate lattice mismatch was fabricated,and its room-temperature detectivity is comparable to that of international commercial InAs photodetectors.
[18] X Marcadet, A Rakovska, I Prevot et al. MBE growth of room-temperature InAsSb mid-infrared detectors. Journal of Crystal Growth, 227, 609-613(2001).
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Ze-Zhong CHEN, Yong-Fei DUAN, Hong-Yu LIN, Zhen-Yu ZHANG, Hao XIE, Yan SUN, Shu-Hong HU, Ning DAI. Liquid Phase Epitaxy (LPE) growth of the room-temperature InAs-based mid-infrared photodetector[J]. Journal of Infrared and Millimeter Waves, 2023, 42(3): 306
Category: Research Articles
Received: Oct. 13, 2022
Accepted: --
Published Online: Jul. 5, 2023
The Author Email: HU Shu-Hong (hush@mail.sitp.ac.cn), DAI Ning (ndai@mail.sitp.ac.cn)