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The problems of in situ ellipsometric control during the growth of ZnTe and CdTe buffer layers intended for cadmium-mercury-tellurium epitaxy are considered. It has been established that for 20 nm ZnTe layers the spectral dependences of the optical constants near the absorption edge are smoothed, which indicates the presence of structural defects in the film. It has been shown that the microrelief of the CdTe growth surface is a criterion for the structural perfection of the layers and can be measured using an ellipsometer both at the early stages and during steady-state growth. [ABSTRACT FROM AUTHOR]

Chemical pretreatment and surface cleaning is a key procedure of semiconductor technologies. Development of methods for the preparation of mercury cadmium telluride (HgCdTe) surfaces is of interest because this material has a wide range of known and potential applications in photoelectronics. This work reports an XPS and AFM study of the effect of various chemical treatments on the chemical composition and micro-morphology of the HgCdTe surface. Among all considered etchants, only ammonium hydroxide effectively removes the native oxide of HgCdTe without leaving a surface layer of metallic tellurium, while preserving nearly stoichiometric chemical composition of the surface. The optimal time of aqueous ammonia treatment is determined. [ABSTRACT FROM AUTHOR]

We investigate the HfO2/Hg0.78Cd0.22Te interface fabricated by plasma-enhanced atomic layer deposition (PEALD) at 120 °C During the deposition of HfO2, no donor-like defects are introduced into mercury cadmium telluride. X-ray photoelectron spectroscopy and ellipsometry were used to establish the optimal process regime at 120 °C and to demonstrate how HfO2 layer composition and growth rate per cycle depend on post-plasma purge time; the optimum is achieved at 6 s. Increasing the post-plasma purge time decreases the carbon and nitrogen impurity concentration in the HfO2 layer. Measurements of the admittance of metal-insulator-semiconductor (MIS) structures over the surface of a sample show that the electro-physical properties are uniform. We discuss the method of measuring the admittance of MIS structures that allows us to minimize the contribution of slow states with trapped charge on shape and shift of the C–V curve. The results demonstrate that the densities of fixed charge, slow states, and fast interfacial traps at the HfO2/MCT interface are greater than that for Al2O3/MCT (also formed by PEALD). The interface trap density is estimated from a normalized parallel conductance map, and the HfO2 film adheres well. [ABSTRACT FROM AUTHOR]

Mid- and long-wave infrared nBn structures based on HgCdTe grown by molecular beam epitaxy (MBE) on GaAs (013) substrates were fabricated. For mid-wave nBn structures, the composition in the absorbing layer was 0.29, and for long-wave nBn structures, this composition was 0.21. The composition in the MBE HgCdTe barrier layers ranged from 0.61 to 0.67. Based on the fabricated HgCdTe nBn structures, test metal–insulator–semiconductor (MIS) devices were created by applying a dielectric Al2O3 film with the thickness of about 90 nm. The admittance of test MIS devices was investigated over a wide range of frequencies and temperatures. An equivalent circuit of MIS device based on MBE HgCdTe nBn structure is proposed, which includes the dielectric capacitance, the capacitance and resistance of the barrier layer, and the series resistance of the absorbing layer bulk. It is shown that the values of the equivalent circuit elements are easy to determine from the experimental frequency dependences of admittance in accumulation mode. Comparison of element values for MIS devices based on mid-wave and long-wave nBn structures is carried out. [ABSTRACT FROM AUTHOR]

Two types of long-wave infrared nBn-structures based on mercury cadmium telluride grown by molecular beam epitaxy on GaAs (013) substrates have been fabricated. For each type of device, the side walls of the mesa structures were passivated with an Al2O3 insulating film or left without passivation. The CdTe content in the absorbing layers was 0.20 and 0.21, and in the barrier layers, it was 0.61 and 0.63. The dark currents of the manufactured devices were studied in a wide range of voltages and temperatures. The values of the surface leakage component are found under various conditions. It has been shown that the surface leakage current density decreases upon passivation with an Al2O3 film. It was found that in the fabricated nBn-structures at room temperature, the surface leakage component dominates at reverse biases, and at forward biases, the dark current is determined by the combined effect of the surface leakage component and the bulk current component. From the Arrhenius plots, the values of the activation energies of the surface leakage current component were found, which are in the range from 0.05 to 0.10 eV at small reverse biases. At small reverse biases, upon cooling the samples, the role of the bulk component of the dark current increases, which at 180 K is approximately 0.81 A/cm2. In the temperature range 200–300 K, the values of the dark current density exceed the values calculated according to the empirical Rule07 model by a factor of 10-100, which indicates the possibility of creating the long-wave infrared barrier detectors by decreasing the values of the surface leakage component. [ABSTRACT FROM AUTHOR]

Mercury cadmium telluride n-Hg1 –xCdxTe (HgCdTe) films with near-surface wide-bangap layers were grown by molecular beam epitaxy on Si(013) substrates. Admittance of the metal–insulator–semiconductor (MIS) structure was measured in samples based on the initial HgCdTe film and the same films after implantation with As+ ions and after subsequent thermal annealing. Methods taking into account the presence of near-surface graded-gap layers and slow surface states were used to determine the main parameters of these layers upon technological procedures involved in the production of photodiodes. [ABSTRACT FROM AUTHOR]

Three types of nBn structures based on mercury cadmium telluride grown by molecular beam epitaxy have been fabricated. As barrier layers in nBn structures, Hg1–xCdxTe at x = 0.67 and 0.84 and the 18 period Hg0.20Cd0.80Te (9 nm) – HgTe (2 nm) superlattice were used. To study the properties of barrier layers based on nBn structures, MIS devices were created using dielectric Al2O3 films. The impedance of the created devices was investigated over wide ranges of voltages, frequencies, and temperatures. Equivalent circuits of MIS devices based on nBn structures in the accumulation mode are proposed. It is shown that measurements of the frequency dependences of the impedance make it possible to determine the values of the differential resistance of the barrier layer in a wide range of conditions. It was found that the values of the differential resistance are determined only by the bulk component of the dark current, and the surface leakage component does not affect the measured impedance of MIS devices. The dependences of the values of the equivalent circuit elements on the area of structures, voltage, and temperature are determined. It is shown that in the temperature range 210–300 K, the values of the differential resistance of the barrier layer based on Hg0.33Cd0.67Te are determined by the diffusion-limited flow of holes from the contact and absorbing layers, at the forward and reverse biases, respectively. The values of the product of the differential resistance and the area are determined for nBn structures with various parameters of the barrier layers. The possibilities of using the measurements of impedance of MIS devices based on nBn structures to study the homogeneity of properties of various layers are demonstrated.. [ABSTRACT FROM AUTHOR]

The results of studying the admittance of unipolar barrier structures based on HgCdTe grown by molecular beam epitaxy (MBE) on GaAs (013) substrates are presented. Using passivation with an Al2O3 insulator, device nBn structures based on HgCdTe were fabricated. The layer parameters in the created structures provided the possibility of detection in the spectral range of 3–5 μm. Based on the analysis of the frequency dependences of the admittance, an equivalent circuit of nBn structures at small biases is proposed. The dependences of the equivalent circuit parameters on the area of the mesa structure and temperature are determined. The properties of high-temperature maxima in the voltage dependences of the capacitance and conductance of nBn structures, which are presumably related to the recharging of surface states at the heterointerface between the barrier and absorbing layers, are studied. It is found that in a wide range of frequencies and temperatures, the capacitance – voltage characteristics of nBn structures based on HgCdTe at reverse biases can be used to determine the concentration of donor impurities in the absorbing layer. It is shown that the admittance of test MIS devices in a mesa configuration, formed on the basis of the MBE HgCdTe nBn structures, is determined by the combined influence of electronic processes in the contact, barrier, and absorbing layers. [ABSTRACT FROM AUTHOR]

A study of defects in HgCdTe films grown by molecular-beam epitaxy on GaAs and Si substrates was performed. Variable-temperature photoluminescence (PL) and carrier lifetime measurements were carried out on as-grown films and films subjected to post-growth annealings. Films grown on GaAs substrates appeared to be mostly free from defects providing energy states within the bandgap, yet specific acceptor states were generated in these films under conditions associated with mercury deficiency. The properties of films grown on Si substrates were mostly governed by two types of uncontrolled defects. Relatively deep levels with energy 40 to 70 meV were revealed with the use of PL measurements, yet their effect on the lifetime was not traced. The lifetime value was rather determined by other type of defects with energy depth of ∼30 meV. Possible relation of these defects to the specifics of MBE growth of HgCdTe on Si substrates is discussed. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Electrical and optical studies of defects in molecular beam epitaxy (MBE)-grown HgCdTe films, undoped and doped with arsenic, were carried out. By comparing results of ion milling-assisted Hall-effect measurements with micro-Raman spectroscopy data, it was shown that the films contained electrically neutral defects related to excessive tellurium. It is suggested that these defects are Te nanocomplexes and that they are typical of the MBE HgCdTe technology. Under ion milling, they get electrically activated by interstitial mercury and form donor centers with concentration of ∼1017 cm-3, which allows for detecting them with measurements of electrical parameters of the material. Also, it can be suggested that in films doped with arsenic with high-temperature cracking, As2 dimers in the arsenic flux react with excessive tellurium and form As2Te3 donor complexes, thus preventing formation of Te nanocomplexes. Arsenic activation annealing may break As2Te3 complexes and release Te, which can again form the complexes under ion milling. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Electrophysical properties of multilayered heteroepitaxial structures of Hg1-xCdxTe with x=0.3-0.4 grown by molecular beam epitaxy on silicon substrates are presented. The passivating effect of thin CdTe layers grown on top of the structures in single process is demonstrated. Comparison between experimental and theoretical temperature dependencies of reverse currents in n-on-p and p-on-n diodes fabricated by boron and arsenic ion implantation in vacancy-doped p-type and In-doped n-type Hg1-xCdxTe films, respectively, are presented. The influence of p-n junction position in double-layer heterostructure on temperature dependencies of reverse currents is examined. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Defects in mercury-cadmium-telluride heteroepitaxial structures (with 0.3 to 0.4 molar fraction of cadmium telluride) grown by molecular-beam epitaxy on silicon substrates are studied. The low-temperature photoluminescence method reveals that there are comparatively deep levels with energies of 50 to 60 meV and shallower levels with energies of 20 to 30 meV in the band gap. Analysis of the temperature dependence of the minority carrier lifetime demonstrates that this lifetime is controlled by energy levels with an energy of ∼30 meV. The possible relationship between energy states and crystal-structure defects is discussed. [ABSTRACT FROM AUTHOR]

The impurity-defect structure of heteroepitaxial CdHgTe/Si (0.35 < x < 0.39) layers grown by molecular beam epitaxy for the creation of arsenic-ion-implanted p- n junctions has been studied by the photoluminescence method. It is established that full realization of the possibilities of p-on- n photodiode structures based on the CdHgTe/Si system is hindered by uncontrolled doping of the material that leads to the formation of both shallow (impurity level energy ∼10 meV) and deep (∼50 meV) acceptor levels. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) of CdHgTe solid solutions subjected to low-energy ion treatment is studied. A blue shift of the peaks in the PL spectra is observed immediately after ion treatment, which is attributed to the formation of a high concentration of donor defects and to the Burstein-Moss effect. The change in the shape of the PL spectra and, in particular, the disappearance of lines associated with transitions to acceptor states indicate that these defects are formed by the interaction of interstitial mercury atoms introduced into the sample during the course of treatment with impurity atoms. As the treatment is terminated, the electron concentration decreases due to the disintegration of defects and the blue shift disappears, but the shape of the spectra remains unchanged. This behavior of the PL spectra can be used for diagnostics of the defect-impurity structure of CdHgTe. [ABSTRACT FROM AUTHOR]

An ion milling-assisted study of defect structure of HgCdTe films grown by molecular beam epitaxy on Si substrates was performed. The films appeared to contain initially neutral Te-related defects with concentration of 1017 cm-3, typical of HgCdTe. The concentration of residual donors was found to be quite low ((3-8) × 1014 cm-3). Specific to HgCdTe/Si technology appeared to be a considerable number of stacking faults, which affected the carrier mobility in n-type material. These defects can be annealed in He atmosphere at 230 °C, and after ion milling the electrical parameters of n-type HgCdTe/Si films approach those of high-quality bulk crystals [ABSTRACT FROM AUTHOR]

Narrow-gap mercury cadmium telluride thin films grown by MBE and LPE methods onto various substrates (HgCdTe/Si, HgCdTe/GaAs, HgCdTe/CdZnTe) were investigated as a piezoelectric heterostructure for IR detection. The photoresponse, infrared transmittance spectra, parameters of the charge carrier transport, and mechanical properties were studied. Mechanical stresses at the layer-substrate interface were analyzed. HgCdTe-based infrared device is considered, operating in the middle (3-5 μm) infrared spectral range without cryogenic cooling to achieve performance level D* = 2.6 · 109w-1cm · Hz 1/2. The possibility to detect infrared radiation is thought to be based on the possibility of the spatial separation of the non-equilibrium carriers in the strained semiconductor heterostructure with piezoelectric properties. [ABSTRACT FROM AUTHOR]

Growth processes were considered for heteroepitaxial structures based on a mercury-cadmium-telluride (MCT) solid solution deposited on GaAs and Si alternative substrates by molecular-beam epitaxy. Physical and chemical processes of growth and defect-generation mechanisms were studied for CdZnTe epitaxy on atomically clean singular and vicinal surfaces of gallium-arsenide substrates and CdHgTe films on CdZnTe/GaAs surfaces. ZnTe single-crystalline films were grown on silicon substrates. Methods for reducing the content of defects in CdZnTe/GaAs and CdHgTe films were developed. Equipment for molecular-beam epitaxy was designed for growing the heteroepitaxial structures on large-diameter substrates with a highly uniform composition over the area and their control in situ. Heteroepitaxial MCT layers with excellent electrical parameters were grown on GaAs by molecular-beam epitaxy. [ABSTRACT FROM AUTHOR]