Blocked Impurity Band Detectors Research Articles

The high-performance linear scan imaging system of terahertz Si-based blocked-impurity-band detector

Terahertz (THz) Si-based blocked-impurity-band (BIB) detector is becoming the overwhelming choice for applications in space-based instruments, airborne, and imaging systems. A high-performance linear scan imaging system based on the THz Si-based BIB detector is designed. Through the optimized design of cryogenic Dewar and a suitable optical system, the imaging system reduces background stray radiation, and then improves the THz imaging performance of the detector. At the temperature of 4.2 K and the bias of 2.6V, the blackbody peak responsivity of the Si-based BIB detector is 23.77A/W, while the dark current is 4.72×10−11 A and the corresponding responsivity non-uniformity is less than 6.8%. Moreover, the experiment results show that the noise equivalent temperature difference (NETD) of the whole system reaches 10mK, and the spatial resolution reaches 50 µm. This work is beneficial to the larger scale array integrated BIB imaging system.

The Anti-Reflection Coating Design for the Very-Long-Wave Infrared Si-Based Blocked Impurity Band Detectors

An anti-reflection coating on a back-illuminated 128 × 128 array Si-based blocked impurity band (BIB) detector in a very-long-wave infrared range was designed in this work. The reflectance and transmittance spectra of ZnS films with different thicknesses on intrinsic Si substrates were studied with a FDTD simulation and experiment. Compared to bare Si substrate, the reflectance of Si coated with 1.5, 2.0, 2.5, and 3.0 μm thick ZnS significantly decreased, while the transmittance increased in the range of 10.0~25.0 μm band. The transmittance enhancement ratio reached approximately 32%, 32%, 28%, and 29%, respectively. It was evidenced that the enhanced transmission at a specific wavelength was caused by the effective interference cancellation effect. Then, a 2.0 μm thick ZnS thin film was deposited on the backside of the 128 × 128 array Si-based BIB detector. The spectral responsivity of the detector increased significantly. Additionally, the blackbody responsivity increased by approximately 36%, suggesting that the ZnS film is an ideal anti-reflection material for VLWIR detectors in the range of 10.0~25.0 μm band.

High-operating temperature far-infrared Si:Ga blocked-impurity-band detectors

Silicon-based blocked impurity band (BIB) detectors have become the preferred candidate for the astronomical observation field because of their excellent ability for far-infrared detection, easy integration with the readout circuit, and potential for large-scale preparation. We fabricate Si:Ga BIB far-infrared detectors by a molecular beam epitaxy technique with an impressive blackbody specific detectivity of 4.21 × 1011 cm Hz1/2 W−1 at 10 K and nearly uniform broadband response between 2.5 and 20 μm. A response mechanism with variable temperature is described minutely by the varying temperature optoelectronic characterization and theoretical calculation as well as energy band diagram. The substantial results indicate that the responsivity of the detector can steadily maintain up to 26 K for far-infrared. This paper not only increases the accessibility of BIB detectors' fabrication tools but also provides an approach of high-operating temperature far-infrared detectors for astronomy explorations.

Wavelength Modulation Characteristics of Metal Gratings on Si-Based Blocked-Impurity-Band (BIB) Terahertz Detectors.

In this work, the wavelength selection characteristics of metal gratings on Si-based blocked-impurity-band (BIB) detectors in the terahertz band were studied by performing experiments and a finite difference time domain (FDTD) simulation. The transmission spectra of metal gratings with different periods on 130 μm intrinsic Si substrates were measured. When the metal grating period increased from 16 to 20 to 32 μm, the peak position of the spectrum moved from 21.71 to 24.50 to 36.59 μm, which is in good agreement with the FDTD simulation results. The structure with the period of 32 μm shows the best wavelength selective transmission characteristics. Then, the bare Si-based BIB devices and metal grating/Si-based BIB hybrid devices with different thicknesses of blocking layers of 2 and 5 μm were fabricated. By covering different periods of metal gratings for the devices with a thicker blocking layer of 2 μm, we obtained more effective wavelength selection characteristics and stronger response spectra enhancement ratios that were about 1.3, 2.4, or 1.9 times. This was mainly due to the localized optical field enhancement effect of the plasmons resonance in metal gratings, which decays exponentially in a vertical direction. Our results demonstrate a new approach for the Si-based BIB detector to realize multiband selective detection applications.

Temperature-sensitive mechanism for silicon blocked-impurity-band photodetectors

Benefit from high quantum efficiency and low dark current, blocked-impurity-band (BIB) detectors have been the state-of-the-art choice in astronomy science. The temperature extrinsic-response-reduction mechanism in BIB detectors is vague for lack of pertinent research. We fabricated Si:P BIB detectors with a remarkable blackbody detectivity of 2 × 1012 cm · Hz1/2/W at 4 K, 2 V (blackbody 800 K). Both varying temperature optoelectronic characterization and calculated results overturn the common standpoint that focuses on ionization proportion. Instead, solid evidence indicates that the increase in the negative charge density according to temperature significantly influences the width of the depletion region until it totally vanishes beyond 20 K. The mechanism enriches the design thoughts of the BIB detector for improving its performance.

Observation of gain operation mode in Ge:B BIB THz detector

Blocked impurity band (BIB) detectors play an important role in astronomical detection from the mid-infrared to THz region. We demonstrated the field dependence of the photoresponse in BIB detectors using both experimental results and theoretical calculations. It was found that there is a gain operation region between the saturation voltage of the photocurrent and the breakdown voltage of the dark current. The photoconduction gain in the gain operation region is several orders of magnitude larger than that in the other voltage range. Considering the field-assisted thermal ionization process and the photon-assisted impact ionization process, the gain operation mode can be well explained. Utilizing the gain operation mode, Ge:B BIB detectors can even detect the objects with a temperature as low as 10 K. We provide a theoretical basis to optimize BIB detectors and further improve their detection performance.

Design, calibration, and application of a cryogenic low-background infrared radiometer for spectral irradiance and radiance measurements from 4 μm to 20 μm wavelength.

We have constructed, calibrated, and tested a cryogenic low-background infrared radiometer for both spectral radiance and irradiance measurements over the 4 μm to 20 μm wavelength range. The primary purpose of the Missile Defense Transfer Radiometer (MDXR) is to measure absolute irradiance or radiance from cryogenic infrared test chamber sources using a photoconductive Si:As Blocked Impurity Band (BIB) detector and a set of spectral filters. The MDXR also includes an absolute cryogenic radiometer (ACR) and a Fourier transform spectrometer (FTS). For irradiance measurements, the ACR is used to provide the primary power scale for the BIB detector in conjunction with spectral filters, while the FTS/BIB configuration derives its scale from an internal blackbody source. The two measurement scales show agreement for the irradiance of highly collimated (< 1 mrad) infrared beams from 10-13 W/μm/cm2 to 10-8 W/μm/cm2 within the combined relative uncertainties of 2.6 % (coverage factor k = 1.) We have also calibrated the radiometer for radiance measurements by using a large cavity fluid bath blackbody that overfills the spatial and angular extent of the radiometer entrance pupil. The radiometric calibration uncertainty analysis of the radiometer as well as its maintenance and stability are discussed.

The research progress of Si-based blocked-impurity-band infrared detecting materials and detectors

<p indent=0mm>Infrared detection possesses a significantly application prospect in the field of astrophysics. Due to the special natures of deep-space exploring objects, the performance of infrared detector is very demanding. Blocked-impurity-band (BIB) infrared detectors, with advantages of wide spectrum coverage, low noise, high sensitivity, good resistance to cosmic particle radiation etc., have become the state-of-the-art choice for astronomical application internationally. The response of BIB detectors ranges from mid-infrared to far-infrared waveband, and the widespread use of BIB detectors help human beings obtain a series of important scientific achievements in the field of deep-space exploration. The research on BIB infrared detector in China started rather late. Even though big progress has been achieved in recent years, it still lags far behind the advanced level globally. This article reviews the research progress for BIB infrared detectors of China in the past <sc>5 years.</sc> The preparation technology, physical property characterization, photoelectric response characteristics of BIB infrared detection material and corresponding devices, and the control of surface plasmon polaritons on the photoelectric response of the detectors are introduced detailly. These provide references and experimental bases for the development of BIB infrared detector in China.

Blocked impurity band very long wavelength infrared detector

Blocked impurity band (BIB) detector is a derivative of the impurity band conduction (IBC) detector. It can detect low-energy photons whose energy is much smaller than the band gap of the semiconductor through the electronic transition on the impurity band. The detection wavelength of the BIB detector is mainly determined by the substrate and doped impurities which can cover the range of 5–300 μm. Owing to the advantages of long detection wavelength, high detection rate and good radiation resistance, BIB detectors have been extensively studied and are widely used in various large-scale astronomical infrared detection platforms. Presently, Si-based BIB detectors are developing rapidly, but the development of Ge-based and GaAs-based BIB detectors is relatively slow. BIB detectors play an irreplaceable role in promoting the development of astronomy and related sciences. Developed countries such as Europe and the United States have invested a lot in scientific research on BIB detectors. With the development of China’s economy and technology, Chinese researchers hope eagerly that the domestic BIB detector can be put into use as soon as possible. Herein, in order to help the related researchers to quickly understand the BIB detector, the device physical model, preparation methods, testing methods and development status have been discussed, and the involved working mechanism and key device technology are also explored.

Corrections to “Optimized Si-Based Blocked Impurity Band Detector Under Alternative Operational Mode” [Sep 19 3891-3895

Unfortunately, we made serious mistakes with the information of the authors in [1] . The e-mail of Weida Hu should be wdhu@mail.sitp.ac.cn. The affiliation address of He Zhu and Weida Hu should be corrected as follows:

Uniformly Broadband Far-Infrared Response From the Photocarrier Tunneling of Mesa Si:P Blocked-Impurity-Band Detector

The silicon-based blocked-impurity-band (BIB) detectors play an irreplaceable role in long-wavelength and far-infrared detection applications from 2 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40~\mu \text{m}$ </tex-math></inline-formula> , especially in astronomy. However, how to remove the anomalous sharp peaks in the spectral response of the planer structures is still unresolved. Here, we propose a tunneling current model to demonstrate the carrier transport mechanism in the planar structures. Specifically, the surface channel induced by dry etching on sidewalls of the mesa structures facilitates the photocarriers to bypass the interface barrier according to the model. Two structures with the same photosensitive area are fabricated and measured to characterize the role of the interface barrier. The disappearance of the sharp response peak at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$31.8~\mu \text{m}$ </tex-math></inline-formula> in the measured photocurrent spectra of the mesa structure well confirms our model. Moreover, the manipulation of the localized energy level of the interface barrier is then utilized to optimize the mesa structure. A much lower dark current of the mesa structures is realized compared with that of the planar ones. Peak detectivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5.6\times 10^{12}$ </tex-math></inline-formula> Jones and uniformly broadband response among 2.5– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40~\mu \text{m}$ </tex-math></inline-formula> are also achieved. We believe the results will find potential applications in the BIB detectors design.

The High-Performance Imaging Verification of Si:P Blocked Impurity Band Detector for Very-Long-Wave-Infrared Spectral Range

Very-long-wave-infrared (VLWIR) photodetectors have attracted great attention from scientists worldwide in the ground and space-based detections, imaging and early warning. However, the application of VLWIR photodetectors on earth is limited by the difficulty of establishing a high spatial-resolution fine imaging system with high-performance detector and large size optical lens. In this work, the VLWIR Si-based blocked-impurity-band (BIB) detector is fabricated and its high-performance imaging system is constructed. The CVD growth progress is optimized by enhancing the doping concentration of absorption layer, and shortening the transition length between blocking and absorption layers. At the temperature of 4.2K, the blackbody responsivity of Si-based BIB detector reaches 20.78A/W and the Noise Equivalent Power is $8.7\times 10^{-16}\text{W}$ /Hz1/2 at 2.6V. Based on the high performance Si-based BIB detector, an imaging verifying system is set up to detect different room-temperature objects. Its spatial and temperature resolution reaches $250~\mu \text{m}$ and 10mK, respectively. Our results indicate that with suitable optical imaging system, the BIB detector is more effective than the infrared detector of commercial thermal infrared imager in detecting room temperature or low temperature objects like metal. Our work is helpful for the further research on the large scale array integrated BIB imaging and detection system used on earth for explosives detection, biological nondestructive detection as well as security check.

Study on the noise characteristics of GaAs-based blocked-impurity-band (BIB) detectors

Terahertz (THz) photodetector has attracted great attention from worldwide scientists for its applications in security check, biomedical treatment, and astronomical observation. In the performance evaluation of the THz photodetector, the noise level is one of the critical parameters. The Gallium Arsenide (GaAs) blocked-impurity-band (BIB) detector, which is fabricated from intrinsic GaAs-based photoconductive detectors, reveals an attractive advantage of low dark current value and high signal to noise ratio (SNR). In this work, the epitaxial GaAs BIB detector was fabricated and its noise behavior under various bias was investigated at the temperature of 3.5 K. The measured noise consists of flicker noise (1/f noise), shot noise, thermal noise and measurement noise. The effect of bias and operation temperature (TOpe) on the noise characteristics of a GaAs-based BIB detector has been studied by numerical simulation for suppressing device noise. According to the simulation, the total noise gradually increases with TOpe, and dominated by the shot noise. Our work may provide useful theoretical support to solve the critical epitaxial growth bottleneck of GaAs BIB detector and improve its performance for the applications of astronomical observation, security check, etc.

Study on the fabrication process and photoelectric performances of si-based blocked-impurity-band detector

The structural model and fabrication process of the Si-based blocked-impurity-band (BIB) detector were proposed. The numerical simulation of phosphorus ion implantation and rapid thermal annealing was investigated. Various implantation conditions were analyzed to meet the requirements of good electrical contact. Moreover, the carrier activation effect of phosphorus ion implantation and rapid thermal annealing was demonstrated by Hall test. Then the relationship between blackbody responsivity and annealing temperature was analyzed. According to the measurement results, the blackbody responsivity and response wavelength range of Si-based BIB detector we fabricated can reach 2.2A/W and 5–45 μm, respectively. Our work shows that the good electrical contact can improve the blackbody responsivity. It provides an effective method to fabricate Si-based BIB detector with good performances.

Impact of the Structural Parameters on the Photoresponse of Terahertz Blocked-Impurity-Band Detectors With Planar Structure

We fabricate germanium-based blocked-impurity-band (BIB) terahertz detectors with the same planar structure but different structural parameters. The photoresponse waveband range is about 40-130 μm. The best detectivity of these detectors reaches as high as 1.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> Jones at 2.6 V and 4 K. The impact of the structural parameters, including the length of the absorbing layer and blocking layer (BL) on the performance of detectors, is investigated. It is concluded that there is an optimum BL length, enabling the fabricated BIB detectors to achieve the highest sensitivity. This work highlights the importance of the optimized structural parameters and their influence on the performance of the detectors.

Temperature-dependent spectral response mechanism in GaAs-based blocked-impurity-band (BIB) far-infrared detectors

Temperature-dependent spectral response mechanism in GaAs-based blocked-impurity-band (BIB) far-infrared detectors has been investigated. Device structure, processing steps and physical models are described in detail. In this work, our discussion is mainly focused on the operation temperature (Tope) of BIB detector. It is demonstrated that the critical Tope and the optimal Tope both exist for GaAs-based BIB detector. It is only when the temperature-assisted photo electron excitation process is fundamentally equivalent to the temperature-assisted photo electron recombination process that the optimal Tope occurs, and it is only when the temperature-assisted photo electron excitation process is dominated by the temperature-assisted photo electron recombination process that the critical Tope occurs.

Optimized Si-Based Blocked Impurity Band Detector Under Alternative Operational Mode

In this paper, alternative operational mode (AOM) of Si-based blocked impurity band (BIB) detectors is thoroughly investigated. The basic structure of the detector evolves from the prototype of the ion-implanted BIB detector, which is potentially compatible with CMOS processes. Benefiting from lower dark current, the detectivity of ion-implanted devices studied in this work is comparable with the Si BIB detectors ever reported. For ion implantation devices, a peak blackbody detectivity of ${5} \times {10}^{{12}}$ cm $\cdot $ Hz1/2/W (background temperature T = 40 K) occurs at 2 V under AOM. These merits make the ion-implanted device a powerful candidate for a wide range of applications from infrared to terahertz band. By analyzing the carrier distribution and the band structure in different functional regions of the device at the measured temperature, depletion junction formed in the region of active layer near active layer/cathode interface side is deduced when the device is operated under AOM. The theory is successfully used to interpret experimental data, including the detectivity comparable to the epitaxial device, significantly reduced dark current.

Design and fabrication of plasmonic tuned THz detectors by periodic hole structures

We predict an extraordinary transmission (ET) of a periodic hole structure (PHS) by simulating plasmonic properties using finite difference time-domain Solutions. The ET effect is used to modulate the photoresponse by integrating the PHS into silicon-based blocked-impurity-band (BIB) terahertz detectors. The measured photoresponses of the experimentally realized PHS + BIB detectors confirm the tunability of photoresponses. Moreover, the electromagnetic field distribution is also simulated, which reveals that the prominent modulation effect originates from a strongly confined electromagnetic field. The response away from the resonance wavelength is largely suppressed. This work demonstrates the potential of our device in multi-spectral terahertz detection.

Evaluation of the compensation ratio of heavily-Ga doped Ge for far-infrared detectors in astronomy

Ge-based blocked impurity band detectors fabricated with the surface-activated wafer bonding (SAB) method are expected to realize larger format arrays for far-infrared astronomical observations. To make sensitive p-type Ge detectors, the minor impurity (ND) concentration of a heavily-impurity doped Ge wafers is required to be <1014 cm−3 in addition to the major impurity (NA) concentration of ∼1016 cm−3. Thus, a compensation ratio K (= ND/NA) below 10−2 should be achieved in advance to SAB. We measured the resistivity and carrier density of heavily-Ga doped Ge wafers at temperatures of 3–300 K. However, ND and NA of the wafers cannot be obtained from the conventional model for p-type semiconductors due to the significant contribution of the impurity band conduction (IBC). Then, an extended model including the IBC process was constructed, which was found to well reproduce the measured data over the whole temperature range. From the values obtained from the model fitting, it is revealed that our heavily-Ga doped Ge wafers show NA ∼ 1016 cm−3 with ultra-low K below 10−3.

Wideband infrared trap detector based upon doped silicon photocurrent devices.

We have designed, fabricated, and measured infrared trap detectors made from arsenic-doped silicon (Si:As) blocked impurity band (BIB) photodetectors. These trap detectors are composed of two detectors in a wedge geometry, with an entrance aperture diameter of either 1 or 3mm. The detectors were calibrated for quantum efficiency against a pyroelectric reference detector using a Fourier transform spectral comparator system, and etalon effects and spatial uniformity of the traps were also quantified. Measurements of the traps at a temperature of 10K show that nearly ideal external quantum efficiency (>90%) can be attained over much of the range from 4 to 24μm, with significant responsivity from 2 to 30μm. The traps exhibited maximum etalon oscillations of only 2%, which is about 10 times smaller amplitude than those of the single Si:As BIB detectors measured under similar conditions. Spatial nonuniformity across the entrance apertures of the traps was about 1%. The combination of high detectivity, wideband wavelength coverage, spectral flatness, and spatial uniformity make these trap detectors an excellent reference detector for spectrally resolved measurements and radiometric calibrations over the near- to far-infrared wavelength range.