Short wavelength and middle wavelength dual color infrared detector were designed and prepared with InAs/Ga(In)Sb type-II superlattices materials. The Crosslight software was used to calculate the relation between wavelength and material parameter such as thickness of InAs, GaSb, then energy strucutre of 100 periods 8ML/8ML InAs/GaSb and the absorption wavelength was calculated. After fixing InAs/GaSb thickness parameter, devices with nBn and pin structure were designed and prepared to compare performance of these two structures. Comparison results showed both structure devices were available for high temperature operation which black detectivity under 200K were 7.9×108cmHz1/2/W for nBn and 1.9×109cmHz1/2/W for pin respectively. Considering the simultaneous readout requirement for further FPAs application the NIP/PIN InAs/GaSb dual-color structure was grown by MBE method. Both two mesas and one mesa devices structure were designed and prepared to appreciate the short/middle dual color devices. Cl2-based ICP etching combined with phosphoric acid based chemicals were utilized to form mesas, silicon dioxide was deposited via PECVD as passivation layer. Ti/Au was used as metallization. Once the devices were finished, the electro-optical performance was measured. Measurement results showed that optical spectrum response with peak wavelength of 2.7μm and 4.3μm under 77K temperature was gained, the test results agree well with calculated results. Peak detectivity was measured as 2.08×1011cmHz1/2/W and 6.2×1010cmHz1/2/W for short and middle wavelength infrared detector respectively. Study results disclosed that InAs/Ga(In)Sb type-II SLs is available for both short and middle wavelength infrared detecting with good performance by simply altering the thickness of InAs layer and GaSb layer.
It was very different between the etching rate of large patterns and narrow grooves on InGaAs/InP materials by inductively
coupled plasma (ICP) technology. With the aim of high etching rate, good morphology, smooth interfaces and fewer
defects, the etching mechanisms of ICP via changing gas flow rate, chamber pressure and RF power have been analyzed.
Some recipes have been found to achieve a narrow stripe and deep groove with good uniformity, interface and morphology
via high etching rate and good selectivity. The different phenomena during etching the large patterns and narrow grooves
have been explained and the sets of parameters have been summarized that is adapted to the array device on InGaAs/InP
materials during the ICP process.
The InGaAs devices has been chosen as new candidate of solid-state low-light devices because of advantages such
as wide response wavelength, high quantum efficiency, high device performance, digitalized readout, high
temperature operation, high reliability and long lifetime. It has gained vital development and application in the
world. 320×256 InGaAs solid-state low-light devices has been prepared and studied, the p-i-n material structure
was grown by MOCVD system. The mesa device structure was chosen and fabricated by inductively coupled
plasma (ICP) method. The detector chip and CMOS readout integrated circuit was bonded by flip-chip bonding.
The FPAs was packaged to Dewar which temperature could be changed by temperature controller. Both
performances of single element device and focal plane arrays were studied in detail. Very simple optics lens was
adopted to show the imaging of 1.064μm laser spot and hand. Study results disclose feasible material growth,
devices processing and high temperature operation characteristics of InGaAs devices.
InAs/Ga(In)Sb type-II superlattice infrared detectors based on mature III-V material and devices technology has lots of advantages such as tunable energy structure and wide response wavelength range, low dark current and high performance under high temperature, etc. It has been chosen as the Third-Generation infrared detector and developed rapidly in recent ten years. In this paper both theoretical and experimental study have been performed to indicate high temperature operation characterization for the InAs/Ga(In)Sb type-II superlattice middle wavelength infrared detectors . Photo-generated carriers, the ratio of photo conductance and dark conductance were calculated by balance equation method. The dependence of I-V, optical response, device detectivity on temperature has been tested and studied to disclose temperature characteristic of the InAs/Ga(In)Sb type-II superlattice infrared detectors. The results verify the middle wavelength InAs/Ga(In)Sb type-II superlattice infrared detectors can operate at high temperature with high performance.
Infrared photodetectors were widely applied in satellite detection, infrared-guided, infrared early warning and infrared imaging and so on. Currently, InAs/GaSb type-II superlattices (T2SLs) photodetectors have been attracted by their unique band-structure and potential applications. In this paper, the InAs/GaSb T2SLs photodetectors in mid-wavelength infrared (MWIR) spectral range were fabricated with p-i-n structure, and the process parameters were optimized. The multilayer structure was grown on GaSb substrate by Molecular Beam Epitaxy (MBE). The active area of this photodetector was 260μm×260μm, and the sidewall of mesa was protected by SiO2 layer. The thickness of adsorption layer was 1060 nm. To reserve more incident area and to avoid the damage caused by welding process, the pad of electrodes were designed under the mesa. A annular electrode was designed to shorten the transmission time of carriers to improve the collection efficiently. The cut-off wavelength λc of the detector was 4.2μm@77K, and the dark current density was measured as 1.07×10-3 A/cm2@Vb=-0.1V. The peak of specific blackbody detectivity (D*) was equal to 1.05×1010 cmHz1/2/W at zero-bias.
With the rapid development of infrared imaging technology, it plays a more and more important role in modern wars. In
this paper, the impact of changes of target, environment and mission on the development of infrared detecting
technology was analyzed. Infrared imaging systems applied in army, navy and air force military weapons abroad were
introduced. Meanwhile, the equipment status with infrared imaging technology in domestic situation was present and
compared. In the end, a brief discussion about the development trend on modern infrared system was given. It is useful
for the development and research on the domestic infrared imaging system.
ZnO thin films doped with aluminum (AZO) were deposited on silicon dioxide covered p-Si (100) substrates by
radio frequency magnetron sputtering, to fabricate AZO/SiO2/p-Si heterojunction, as an absorber for ultraviolet cell. The
optical and electrical properties of the Al doped - ZnO films were characterized by UV-VIS spectrophotometer, current-voltage
measurement, and four point probe technique, respectively. The results show that AZO films have good quality.
The electrical junction properties were investigated by I-V measurement, which reveals that the heterojunction shows
typical rectifying behavior.
The relationship between the dark conductivity (σd) and temperature (T) of amorphous HgCdTe films has been
investigated at 80-300 K. The measurement of σd as a function of T indicates the presence of four distinct regions: (I)
For 250K≤T<300 K(3.3<1000/T≤4.0), σd is strongly increase with T increasing, the transport mechanism is dominated
by extended state conduction, (II) for 180K≤T<250 K(4<1000/T≤5.6), σd is linearly increase with T increasing, hopping
conduction between localized band tail state dominates the transport mechanism, (III) for 120K≤T<180K
(5.6<1000/T≤8.3), σd is very small and weakly increase with T increasing, constant-range hopping conduction in
localized states near the Fermi energy significantly contributes to the transport properties, and (IV) 80K≤T<120K
(8.3<1000/T≤12.5), the dark conductivity of amorphous HgCdTe films is very small and weakly decreases with
temperature increasing, it would be possible that the conductivity type of amorphous HgCdTe films converted about
120K, i.e. from the n type converted to p type. The temperature behavior of σd of amorphous HgCdTe was described in
terms of the Mott-Davis model.
We present a systematic theoretical study on optical properties of short-period InAs/GaSb type-II superlattices (SLs)
which can serve for Mid-Infrared (MIR) detection. From the energy dispersion relation for the electron derived from
using the standard Kronig-Penney model we calculate the
electron-minibands structure in InAs layer and the
hole-minibands structure in GaSb layer of such SLs. The obtained
band-gap energies are in line with those realized
experimentally. On the basis of the mass-balances equations derived from the Boltzmann equation, at the same time
considering the polarization direction of the infrared irradiation vertical to the growth direction of the material, we
develop an approach to calculate the Fermi level and photo-excited carrier density in the corresponding SL systems. The
dependence of photo-conductivity in InAs/GaSb type-II SLs on temperature and well-widths are examined. This study is
pertinent to the application of InAs/GaSb type-II SLs as uncooled MIR photodetectors.
320×256 GaAs/AlGaAs Quantum Well Infrared Photodetector (QWIP) Focal Plane Array (FPA) was successfully
prepared. The material design, device fabrication, performance measurement, as well as thermal imaging by the first
QWIP FPA thermal imager was addressed in this paper. Further development and application of large format QWIP FPA
detector was also presented. Based on the mature material growth and devices processing technology the large format III-V
QWIP focal plane array was characteristic of promising mass production ability with high performance, good
repeatability, good uniformity and low cost. Besides, the flexible Energy-Band Engineering of III-V QWIP technology
made QWIP FPA as the advanced Third-Gen infrared detector technology now and in the future.
Short wavelength Hg1-xCdxTe infrared detectors were novelly fabricated by loophole technique basing on Liquid Phase Epitaxial materials, rather than conventional ion implantation technology. The Hg1-xCdxTe material was p type doped by Hg vacancy. The formed sensitive area is an annulus centered on the circular junction. The dimension of the annulus depends on the diffusion lengths of minority carriers in both the p and n regions. Laser Beam Induced Current (LBIC) signals of Scan Laser Microscope measurement were used to determine the key parameters such as the minority diffusion length, the size of both n type and p type regions as well as uniformities of the arrays. Good uniformities were observed for the 4×4 HgCdTe photovoltaic arrays by LBIC signals analysis. Furthermore, exponential decays in LBIC signals revealed average minority carrier diffusion length in p type region was around 9 micron, and the average diameter of the n type annulus was 17 micron. The I-V characteristic measurement of the photodiodes determined average zero bias dynamic resistance R0 which was 1.2E9Ω, and zero bias dynamic resistance junction area product R0A was calculated to be average 7.02E3Ωcm2. Further investigations have been performed for the electro-optical performance examination. Infrared spectral response measurement results showed peak wavelength lay around 2.2 micron with cutoff wavelength about 3.5 micron under temperature 77K, average blackbody detectivity D* was 1.71E10cm Hz1/2W-1.
Experiments were designed for analyzing effects of annealing on surface properties of P-type Hg1-xCdxTe Liquid Phase Epitaxy (LPE) films. Owing to special surface characteristics of P-type Hg1-xCdxTe material, it is necessary and vital to obtain good passivation layer for both high performance photoconductive type and photovoltaic type Hg1-xCdxTe detectors. Variable magnetic-field Hall measurement was used to investigate surface properties in temperature range from 1.5 to 200 K for the annealed and unannealed samples. Different temperature behavior of Hall coefficient (RH) was observed for the two kinds of samples. Surface electrons were observed existing for unannealed samples judging by the low temperature characteristic of RH (below 10k). In addition to this, C-V measurement of MIS devices made of same annealed and unannealed sample was also used to analyze the effects of annealing. In the C-V measurement applied bias to which annealed samples could bear was larger than that to unannealed one. Meanwhile, fixed charge density in passivation layer of the annealed samples was smaller than that of the unannealed samples. The above results implied surface charge density on the surface of p-Hg1-xCdxTe material was reduced by annealing treatment comparing with that without annealing. On conclusion, annealing improved surface status of P-type Hg1-xCdxTe material.
The B+ ion implantation technology has been utilized to fabricate the n+ on P HgCdTe photovoltaic arrays with the HgCdTe epitaxial materials grown by Liquid Phase Epitaxial method. The effects of the implanting energy and dose on doping profile and approximate junction depth were calculated in detail, the calculated results are well consistent with the measurement results by the Second Ion Mass Spectrum experimental technique (SIMS). The 10×10 photodiode arrays in which each pixel size is nominally 20×20 μm2 and the pitch is 30 μm were made to investigate the electro-optic performance of devices. The device characterization such as array uniformity and optical crosstalk was non-destructively investigated by the technique of a scanning laser microscope. The two dimensional maps of Laser beam Induced Current (LBIC) signal have shown the good uniformity for the fabricated arrays, and there is no optical crosstalk between the arrays for the used B+ ion implantation conditions at the implanting energy of 130Kev and the dose of 2E14cm-2. The primary performance of photodiodes the zero bias dynamic resistance junction area product R0A, infrared response spectrum, and the detectivity D* have been measured, and the typical values for the test photodiodes with cutoff wavelength of 9.2 μm measured at 77K are: R0A=13.5Ω·cm2, average blackbody detectivity D* =7.18E10cm.Hz1/2W-1.