Extensive material and device statistics of performance and reproducibility are presented to show the maturity of this technology. The demonstration vehicles to monitor yields during this demonstration were long-wavelength infrared (LWIR) HgCdTe multilayer wafers with 128 X 128 detector arrays. The heterostructure photodetectors were of the p-on-n planar configuration. Device data show that MBE LWIR diode test structures have performance that equals that of p-on-n double heterostructure photodiodes made by LPE. Due to the special attention given to understanding and reducing epilayer growth-induced defects, we have achieved improvements in FPA operability values from 92% to 98%. These improvements have resulted in the demonstration of a 128 X 128 FPA hybrid that had detectivity (D*) background limited performance when operating at 80 K in a tactical background environment. Mean D* was 1.28 X 10¹¹ cmHz^1/2/W. The corresponding mean NE(Delta) T was an excellent 5.9 mK.

Long wavelength Si_1-xGe_x/Si heterojunction internal photoemission (HIP) infrared detectors have been successfully demonstrated utilizing the growth of degenerately boron doped Si_1-xGe_x layers on Si. Recently, Si_0.7Ge_0.3/Si HIP detectors with either a Si_1-xGe_x single layer or a Si_1-xGe_x/Si multi-layer have been demonstrated with cutoff wavelengths out to 23 micrometers . Near-ideal thermionic emission dark current characteristics were measured and the electrical potential barriers were determined by the Richardson plot. A photoresponse model, similar to the modified Fowler Equation has been developed for the Si_1-xGe_x/Si HIP infrared detector at wavelengths corresponding to photon energies less than the Fermi energy. The optical potential barriers, the corresponding cutoff wavelengths, and the emission coefficients, C₁, for the HIP detectors have been determined from the measured spectral responses using the photoresponse model. Similar optical and thermal potential barriers were obtained.

Recent progress for in situ monitoring of MCT growth is reviewed with particular reference to the need for improved control and reproducibility of the vapor phase growth methods. RHEED continues to be the main in situ monitor for MBE growth, giving both surface structure and growth rate data. However, this is now becoming supplemented by optical in situ monitors such as ellipsometry and new techniques for measuring the substrate temperature which critically affects the growth quality on the preferred (211)B substrate orientation. The lack of in situ monitoring techniques is no longer a disadvantage for MOVPE with reflection difference spectroscopy and surface photo-adsorption spectroscopy for surface characterization and spectroscopic ellipsometry and reflectometry for layer characterization. Organometallic concentration monitoring has been achieved using Epison ultrasonic monitors and has proved to be a vital part of the growth system monitoring to control critical parameters such as VI/II ratio. Recent results on feedback control of both IMP and direct alloy growth show that improved control is now possible in the complex MOVPE growth environment.

Deep-level transient spectroscopy (DLTS) measurements were performed on midwavelength p⁺n HgCdTe mesa diodes grown by LPE and p⁺n HgCdTe planar heterostructures grown on CdZnTe wafers by MBE. The DLTS spectra of the MBE samples showed the presence of at least two hole traps, while at least two shallower electron traps were observed from the LPE samples. In addition to DLTS measurements, the diodes were also studied using double correlation DLTS (DDLTS) and current transient spectroscopy (CTS). The DDLTS spectra showed sharper peaks than the corresponding DLTS spectra. CTS measurements complement the DLTS data in the temperature range where the diode's leakage current is too high for capacitance measurements. These measurements revealed the presence of additional trapping centers in the LPE samples studied. This paper discusses the interpretation of these results and the suitability of the DLTS technique for the study of point defects in HgCdTe.

The optical absorption coefficient of CdZnTe in the near and mid infrared spectral regions was measured at room temperature using FTIR transmission spectroscopy for several x-values in Cd_1-xZn_yTe grown by the horizontal Bridgman technique as well as for CdTe and ZnTe. The compositional dependence of the absorption coefficient near the band edge was used to determine the composition of bulk CdZnTe, an important material parameter in its application as a substrate for HgCdTe epitaxial growth. In the mid IR range, we find that the wavelength dependence of the absorption coefficient could be varied by adjusting the stoichiometry of the material, i.e., by annealing under various Cd overpressures. The shape of the mid IR Fourier transform infrared spectra is related to the type and the concentration of the free carriers as well as the resistivity of the material. For n-type material, the wavelength dependence of the absorption coefficient can be described by free carrier absorption.

Surface plasmons polaritons (SPPs) may be supported on the surface of PtSi electrodes in PtSi/Si Schottky barrier diodes. Using a prism-air gap-PtSi/p-Si or Otto coupling configuration we have excited SPPs at temperatures below 120 K on these devices. Changes in the dip in reflectance associated with SP excitation indicates changes in the PtSi optical data as a function of temperature. However it is important to understand what the optical data describe. In general they incorporate a surface roughness layer and are not truly characteristic of the material (PtSi) itself. In this context AFM analysis of the surface topography is presented. In addition the compositional structure of the PtSi as determined from Rutherford Backscattering Spectroscopy is discussed.

A non-contact, accurate measurement technique to characterize cross talk in Si infrared photodiode detector arrays using a scanning laser beam of 1-micrometers in spot size is presented.

The interaction between Mercury Cadmium Telluride (MCT) and single pulse of Nd:YAG laser with 1.06 micrometers wavelength and 10 ns pulse duration was studied. The impulse delivered to MCT sample was measured by using ballistic pendulum method. The experiment shows that the momentum transfer results from material being ejected from MCT surface under the impinging of intense pulse laser. The impulse coupling coefficient of MCT gets to its maximum 14.3 dyne(DOT)s/J when incident laser power density is about 7.6 X 10⁸ W/cm². By using 1D model of gas-dynamics, the impulse coupling coefficients have been calculated. The calculated results agree well with measured ones in the region of incident power density larger than 1.5 X 10⁹ W/cm².

The HgCdTe films had been made by vacuum evaporation. If the substrate temperature is about at 100 degree(s)C, the size of the crystallite of the HgCdTe films is about 0.1 micrometers , the size decrease with the substrate temperature decreasing in the range down to about 50 degree(s)C. We had been measured the optical and electrical properties of HgCdTe films, the conductivity is about (0.1 - 1) (Omega) ^-1(DOT)cm^-1 at 300 degree(s)C for polycrystal samples, and the conductivity decrease with the temperature decreasing, the optical gap for one typical sample is about 0.8 eV calculated from the optical absorption edge, the refraction and attenuation index are measured by ellipsometry and the dispersion curves are obtained.

In this paper, the measurement results of n and k of MCT and PST by polarized reflectometry are reported. The results show that in the infrared spectrum region the polarized reflectometry is also an effective method for measurements of n and k.

The surface morphology of HgCdTe wafer irradiated by a single pulse from a Nd:YAG laser (wavelength 0.53 micrometers , pulse width 10 ns) is studied in this paper. The surface structures are related to surface acoustic standing waves, bulk acoustic waves, Hg atoms depletion and boiling of melting surface layer. A plot of damage site area versus pulse laser energy density have been given.

The refractive index and extinction coefficient of Hg_1-xCd_xTe prepared by polishing/etching are studied at liquid-nitrogen and room temperatures with null ellipsometric spectrum method over the visible light region, and reflectance is calculated from Fresnel reflectivity formula and show good agreement with experimental results from reflectivity spectra in the visible light region. Similar experiment is done for Hg_1-xCd_xTe sample prepared by anodic oxidation. The near infrared reflectivity spectra of Hg_1-xCd_xTe are measured at room temperature for three samples with different technological process: polishing, anodic oxidation and passivation with ZnS. The experimental results are compared and discussed.

The rates of growth on oxide films on polished Hg_1-xCd_xTe surfaces exposed to room air are obtained by measuring the ellipticity of polarized light reflected from the surfaces with the ellipsometer. Plots of thickness vs. the logarithm of the time in room air are linear after about 1500 minutes with slopes of 15 angstroms/decade. Immediately after polishing the native oxide film is proximately 10 angstroms thick and increase in thickness by about 36 angstroms after one week. Measurements utilizing polarized light are made of the increase in film thickness with time on Hg_1-xCd_xTe surfaces immersed in water. The regular of the anodization voltage versus time was given. With ellipsometer, the thickness of anodic oxides film grown on Hg_1-xCd_xTe is determined. Further details and discussion will be presented.

In this paper we present an experimental investigation of the performance of GaAs/AlGaAs multiple quantum well photodetectors. The purpose of this exercise was to independently evaluate and verify the responsivity of the GaAs/AlGaAs quantum well infrared photodetectors developed at the Industrial Microelectronics Center in Sweden. These devices use 2D gratings to couple radiation into the detectors and a cladding layer to enhance the coupling of radiation. The devices were of two types: those optimized for high detectivity, and those optimized for high quantum efficiency. The tests performed on these devices included measurement of optical responsivity vs. bias, spectral response, Detectivity (D^*), and measurement of cross-talk between pixels. Several interesting observations were made during the investigation and will be reported in the paper.

Lead chalcogenides are well-known photoconductors in the infrared region. Lead sulfide detectors occupy an important position among infrared detectors owing to their high sensitivity in the near infrared region (1 - 3.2 microns), room temperature operation, low noise and ease of preparation. In this paper, we report for the first time the preparation of infrared sensitive photoconductive lead sulfide films by the swab plating technique. Adherent, non-porous `p' type lead sulfide films of thickness 3 - 4 microns were obtained. These films, after heat- treatment at 550 degree(s)C, showed a dark resistance of 25 - 30 kilo-ohms with a photosensitivity of 0.28. The films have been characterized by XRD, optical and photoconductivity measurements.

Infrared imaging technology has matured dramatically in the past several years and the progress of this technology is reflected in many ways. Staring array format size has progressed in parallel with the growth in size of dynamic random access memory. Chip interfaces are being simplified and in some cases the output format is directly compatible with RS 170 video standards. At the same time, new chip functions such as pixel selection and electronic zoom are being incorporated on the focal plane. Operational temperatures have been increased to 180 K for 5 micrometers medium wavelength staring sensors, and in a few years uncooled 8 to 12 micrometers long wavelength sensors will be commonly available. New quantum well materials technology based upon III-V semiconductors has been rapidly developed to give imaging demonstrations for comparison with PtSi, HgCdTe and InSb. PtSi and InSb commercial infrared imaging cameras are now widely available. InSb, HgCdTe, and extrinsic silicon technology has emerged from demanding military applications to support astronomy needs for more efficient use of precious telescope time. The support of key producibility contracts has resulted in a significant decrease in sensor cost.

A comparison of photovoltaic HgCdTe/Al₂O₃, HgCdTe/CdZnTe, InGaAs/InP and photoconductive GaAs/AlGaAs quantum well infrared photodetector detector technologies has been conducted at Rockwell by exploiting the ability to selectively hybridize disparate mosaic detector arrays to an assortment of silicon multiplexers. Hybrid FPA characteristics are reported as functions of operating temperature from 32.5 K to room temperature and at photon backgrounds from approximately equals 10⁶ to mid-10¹⁶ photons/cm²-sec. The staring arrays range in size from about sixteen thousand to over a million pixels. Background-limited detectivities significantly exceeding 10¹⁴ cm-(root)Hz/W were achieved.

Integrated two-color detector arrays offer significant system advantages (over separate arrays for each color) where two-color information is required. Using a single array with co-located spectral band sensitivities guarantees perfect pixel registration between the two different spectral band images. These two-color IR detectors can be made in HgCdTe using a pair of back-to-back-diodes incorporated in a triple-layer heterojunction (TLHJ). Use of HgCdTe allows any combination of bands between SWIR and LWIR. TLHJs can be operated in either a sequential or simultaneous mode by leaving the layer common to the two diodes floating or by contacting it. The effect of the choice of spectral bands on the meaning of sequential and simultaneous operation is discussed. State-of-the-art trend line performance for each spectral band of a TLHJ has been demonstrated using an all-LPE HgCdTe technology at SBRC. Mean MWIR R_rA of 2 X 10⁷ (Omega) -cm² and LWIR of 1.6 X 10³ (Omega) -cm² have been shown. Quantum efficiencies are typical of trend line PV HgCdTe. Very high quality imaging has been demonstrated using 64 X 64 sensor chip assemblies in a sequential mode incorporating the above TLHJs. Simultaneous detectors have been made in miniarrays and test structures of various size unit cells. 128 X 128 simultaneous arrays are under study. Imaging and test results (performance and uniformity) for each band are comparable to state-of-the-art single-color HgCdTe arrays.

The SPRITE (Signal Processing in the Element) detector comprises a long thin filament of mercury cadmium telluride. The filament is divided into two sections, the integration and readout regions. Ambipolar drift speed in the filament is matched to the scanning speed in a thermal imager, and the device performs in the element the functions normally achieved with time-delay-and-integrate electronics. We consider the optimum choice of integration section length having regard to the trade-off between high and low spatial frequency performance. The readout section length can also be optimized, in this case the noise performance of the detector preamplifier is an important consideration, because both noise and responsivity of the detector fall at high frequencies.

Monte Carlo simulations of the cross talk due to minority carrier diffusion in back illuminated InSb matrices are presented. These calculations are done in three dimensions, and accurately take into account the non-uniform boundary conditions on the front surface. Values of the cross talk for first, second, and third nearest neighbors are obtained along with the theoretical quantum efficiencies for a variety of device geometries and material parameters. In particular, the dependence of cross talk and quantum efficiency on junction size and pitch, for both planar and mesa diodes with and without guard rings is derived. The effects of material and processing parameters such as minority carrier lifetime and diffusion length, surface recombination velocity, absorption coefficient, and InSb layer thickness are also shown. Results of these simulations show that the quantum efficiency and cross talk are strongly dependent on the surface recombination velocity and matrix dimensions, however they are relatively insensitive to the material parameters over a wide range of values. Calculated point spread functions are presented for selected cases, and are seen to display an interesting `nearest neighbor guarding' effect.

Texas Instruments has developed a low-cost, manufacturable uncooled IR focal plane array detector technology. A detector array comprises 245 X 328 pixels on 48.5 micrometers centers. Operating near ambient room temperature, ferroelectric Barium Strontium Titanate (BST) pixels hybridized with a Si read-out integrated circuit consistently yield devices with system noise equivalent temperature difference less than 0.08 K with f/l optics. The fabrication process for forming these arrays is 95 percent compatible with standard Si processes. Detector process commonality with a Si wafer processing format is maintained by fabricating 100 mm diameter ceramic BST wafers with excellent dielectric properties. Highly dense, sintered ceramic BST offers cost and performance advantages not found in single crystal materials. This detector scheme provides forward-looking infrared technology for many applications where cost, weight, power, reliability, and size are important design considerations. Typical applications are surveillance devices, fire control sights for man- portable weapons, and vehicle driver's aids.

We present the performance characteristics of two examples from a special class of photon detector, based on the blocked impurity band (BIB) concept. Recent results are presented on Si:Sb BIB detectors covering the 2 to 50 micrometers wavelength range, and on Ge:Ga BIB detectors that are sensitive in the 50 to 220 micrometers range. The inherent properties of these BIB detectors make them a natural choice for infrared astronomy; minimal sensitivity to ionizing radiation, compatibility with large format (128 X 128) arrays, low dark currents and high detective quantum efficiencies, combined with a lack of anomalous behavior. The detector characteristics are discussed in terms of a standard BIB performance model. Both detector types appear to have unique potential for astronomy applications.

There are several responsivity and gain models adequate to MQW detectors. All are related to two fundamental properties: the escape efficiency of a photo-excited carrier out of the well boundary (P_out) and the capture (or crossing) probability (P_c or P_w equals 1-P_c). In this work we present a rigorous calculation of the escape and capture probabilities based on a Quantum Mechanical approach. In this vicinity of the well the electrons are treated as Gaussian Wave-Packets. The simulation calculates the quantum mechanical reflections encountered by the packets at the interfaces as a function of kinetic energy and applied electric field. The relaxation processes into the bound sub-level are taken into account by introducing an imaginary potential. The simulations are carried out on both stepped and rectangular structures. The step reduces the dwell time above the well and hence the capture probability. This result is in good qualitative agreement with responsivity measurements on such structures. The effects of interface charge and non-uniform charge distribution are also considered. We assume an accumulation of negative sheet charge on the `inverted' interface facing the substrate. This excess charge, introduced during the growth sequence, induces structural asymmetry. The modified well potential is calculated self-consistently and results in an increased barrier height for carriers propagating towards the substrate. Those results are consistent with the asymmetrical responsivity and noise characteristics measured by various groups.

A metal-insulator-semiconductor device, Auger spectroscopy and infrared absorption spectrum have been used to study the impurities in phosphorosilicate glass (sio₂/SPG/sio₂)/InSb. The hydroxyl ions which caused current leakage during high vacuum outgassing were investigated. The current leakage mechanism in InSb p/n diodes have been discussed. The reasons for hydroxyl ions remaining in the passivation films were mentioned.