Mercury cadmium telluride (Hg1_xCdxTe) is widely utilized for infrared detection applications. However, the quality of the surface and the presence of interface defects significantly impact device performance, so further improvements in surface passivation are still necessary. In this study, we explore the use of plasma-enhanced atomic layer deposition (PE-ALD) to deposit HfO2 as a passivation layer for HgCdTe in the temperature range of 80-160 degrees C. The insulating film, semiconductor surface, and their interface are characterized using spectral ellipsometry, X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), atomic force microscopy (AFM), electron microscopy, and capacitance-voltage (C-V) methods. XPS analysis reveals that the fraction of impurities in the HfO2 films significantly decreases at higher deposition temperatures. Simultaneously, changes in the surface composition of HgCdTe become more pronounced. The bandgap width of HfO2 and the insulator-semiconductor interfacial band discontinuity are estimated using EELS and XPS. The surface morphology of the deposited coatings closely resembles that of the underlying HgCdTe. The permittivity of the insulator and the effective fixed charge strongly depend on the deposition temperature. Our findings demonstrate that low-temperature PE-ALD HfO2 effectively passivates the HgCdTe surface, and we propose an optimal deposition temperature for the further development of HgCdTe-based devices.

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.

Metal–insulator–semiconductor (MIS) structures have been made on narrowband n- and p-Hg 1−x Cd x Te(x ≈ 0.22) preliminary chemically cleaned and then oxidized in remote oxygen plasma. Plasma was supplied by an RF generator within a commercial system for plasma-enhanced atomic layer deposition (PE-ALD). An Al 2 O 3 insulating film was deposited on prepared HgCdTe in this system without exposing samples to the ambient atmosphere. HgCdTe epitaxial films comprising or not a surface graded-gap layer (SGGL) have been examined, to reveal its contribution to the electrical properties of the structures. Obtained MIS C–V characteristics reveal near-ideal low-frequency behavior with weak stretching and a narrow hysteresis loop due to low densities of fast and slow surface states. The effective insulator fixed charge has a negative sign with a density of ~1∙10 12 cm −2 . There is no "p-to-n" conductivity type conversion in the structures on HgCdTe grown without the SGGL. The obtained results can be useful for development of HgCdTe-based devices. The proposed passivation approach is compatible with a technology of HgCdTe focal plane arrays (FPAs) manufacturing.

A comprehensive study of the annealing effect (300-400 degrees C) on the electrical properties, morphology and chemical composition of the Au/Pt/Ti/n-InAlAs interface (Schottky contact) is carried out. It is shown that the Schottky contact pre-annealing during the formation or primary short (-1 min) annealing significantly increases the barrier height to the standard 0.68-0.7 eV with an ideality factor close to 1.1 due to the formation of a homogeneous amorphous TiAs layer with a small metallic (elemental) indium content. A further annealing at temperatures 300-350 degrees C for up to 20 min does not lead to significant changes in the morphology and electrical parameters of the Schottky contact. The annealing at the temperature of 400 degrees C (-10 min) leads to an increase in the barrier height and the ideality factor to the values of 0.73 and 1.3, respectively. In this case, the formation of an about 20 nm thick TiAs layer and indium clusters shaped as a pyramids at the Ti/InAlAs interface is also observed. Analysis of the temperature dependences of Schottky barrier parameters within the Tung model showed that only structural changes at the interface after the 400 degrees C annealing lead to a significant increase in the Ti/InAlAs Schottky contact homogeneity, reducing the density of local regions with a lowered barrier height.

Предварительная химическая обработка и очистка поверхности является одной из ключевых операций в полупроводниковых технологиях. Развитие методов подготовки поверхности теллурида кадмия–ртути (КРТ, HgCdTe) является актуальной задачей в связи с широким спектром существующих и потенциальных применений этого материала в фотоэлектронике. С помощью методов РФЭС и АСМ в работе исследовалось влияние различных химических обработок на химический состав и микрорельеф поверхности HgCdTe. Среди всех рассмотренных травителей только водный аммиак эффективно удаляет собственный оксид КРТ, не оставляет поверхностного слоя металлического теллура, и обеспечивает близкий к стехиометрии химический состав поверхности. Предложено оптимальное время обработки в водном аммиаке.

The interface between Cd 0.22 Hg 0.78 Te and HfO 2 grown by plasma-enhanced atomic layer deposition at a temperature of 120 o C in a specifically optimized deposition mode has been studied. The method used in this work for measuring the admittance of metal-dielectric-semiconductor structures made it possible to establish that their electrophysical parameters are uniform over the sample surface. The spectrum of fast surface states density at the HfO 2 -Cd 0.22 Hg 0.78 Te interface has been calculated. Keywords: CdHgTe, HfO 2 , ALD, C-V, passivating coating.

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.

Capacitance--voltage characteristics of metal dielectric semiconductor structures with atomic layer deposition Al2O3 on n- and p-Cd0.22Hg0.78Te (with and without a surface graded-gap layer) preliminary oxidized in oxygen glow discharge plasma (with the resulting oxide thickness of 2 nm) have been studied. The obtained structures reveal the positive fixed charge with a density of ~(1-6)·1011 cm-2. The ratio between a slow surface states density and a surface band gap width is almost independent on graded-gap layer presence, with the value of ~(4-8)·1011 cm-2·eV-1. The proposed passivation approach provides near-ideal low-frequency capacitance-voltages characterized by weak influence of fast surface states. Films of CdHgTe grown without the graded-gap surface layer are proved to be much more sensitive to the process of oxidation in glow discharge plasma. Keywords: mercury cadmium telluride, film, surface states, plasma.

Capacitance−voltage characteristics of metal dielectric semiconductor structures with atomic layer deposition Al2O3 on n- and p-Cd0.22Hg0.78Te (with and without a surface graded-gap layer) preliminary oxidized in oxygen glow discharge plasma (with the resulting oxide thickness of 2 nm) have been studied. The obtained structures reveal the positive fixed charge with a density of ∼ (1−6) · 10^11 cm^(−2). The ratio between a slow surface states density and a surface band gap width is almost independent on graded-gap layer presence, with the value of ∼ (4−8) · 10^11 cm^(−2) · eV^(−1). The proposed passivation approach provides near-ideal low-frequency capacitance-voltages characterized by weak influence of fast surface states. Films of CdHgTe grown without the graded-gap surface layer are proved to be much more sensitive to the process of oxidation in glow discharge plasma.

This paper describes a technique that makes it possible, by analyzing the capacitance-voltage characteristics of metal-insulator-semiconductor or metal-semiconductor structures, to determine the concentration of the background donor impurity in undoped i-In0.53Ga0.47As layers with a thickness less than the width of the space charge region in the near-surface region of the semiconductor in strong inversion mode.

This paper describes a technique that makes it possible, by analyzing the capacitance-voltage characteristics of metal-insulator-semiconductor or metal-semiconductor structures, to determine the concentration of the background donor impurity in undoped i-In0.53Ga0.47As layers with a thickness less than the width of the space charge region in the near-surface region of the semiconductor in strong inversion mode. Keywords: InGaAs, MIS structure, capacitance-voltage characteristic, dopant, space charge region.

The properties of thin HfO 2 films grown by plasma-enhanced atomic layer deposition on Si substrates at various temperatures 80,120, and $160^{\circ} \mathrm{C}$ are studied in this work. For each temperature, the dependences of the growth rate per cycle on the post-plasma pumping time were determined. For the majority of temperatures, saturation of the growth rate per cycle depend of the post-plasma purge time was observed. Accordingly, the optimal times of growth stages were determined for temperatures 80,120, and $160^{\circ} \mathrm{C}$. Studies of the chemical composition of the HfO 2 film by the XPS method showed that hafnium is bound to oxygen,and increasing of the post-plasma purge time reduces the content of suchimpurities as nitrogen and carbon. The electrophysical properties of HfO 2 films have been measured: such asthe capacitance, the dielectric constant and theleakage current density. The values of the built-in charge in HfO 2 film were 2.92 and $2.08 \times 10^{-7} \mathrm{C} / \mathrm{cm}^{2}$ for growth temperaturesof $120^{\circ} \mathrm{C}$ and $160^{\circ} \mathrm{C}$, respectively. The dielectric constant for the HfO 2 film was 10.8 and 11.8 for temperatures of 120 and $160^{\circ} \mathrm{C}$, respectively.

The interface between Cd0.22Hg0.78Te and HfO2 grown by plasma-enhanced atomic layer deposition at a temperature of 120 ℃ in a specifically optimized deposition mode has been studied. The method used in this work for measuring the admittance of metal-dielectric-semiconductor structures made it possible to establish that their electrophysical parameters are uniform over the sample surface. The spectrum of fast surface states density at the HfO2 - Cd0.22Hg0.78Te interface has been calculated.

Теллурид кадмия–ртути (КРТ, CdHgTe), используемый для изготовления многоэлементных фотоприемных устройств (МФПУ) с краем поглощения вплоть до дальнего ИК диапазона, а также обладающий перспективой применения и в терагерцовом диапазоне, характеризуется высокой чувствительностью к внешним физическим, химическим и термическим воздействиям. Нарушение структуры поверхности полупроводника и изменение его химического состава при проведении технологических операций по изготовлению приборов приводит к возникновению электрически активных дефектов, ухудшающих характеристики этих приборов. В связи с этим стабилизация и пассивация КРТ являются одним из ключевых технологических процессов при изготовлении МФПУ [1], разработка и развитие которого не прекращается и по сей день [2].

Metal-insulator-semiconductor structures with atomic layer deposited (ALD) Al2O3 and ultra-thin native oxide were formed on n-type variband Hg1-xCdxTe of two different volume compositions x, referred to as MWIR and LWIR. It is shown that presence of native oxide prior to plasma-enchanced ALD process and origination of this oxide are crucial to properties of an insulator-semiconductor interface. Ultra-thin native oxide formed in glow discharge or remote RF plasma is much more stable than oxide formed during storage of sample in air and provides significantly improved interface quality. The positive sign of fixed charge introduced by plasma oxide is more preferable for an n-type semiconductor than the negative one, but obtained density of fixed charge up to 1 x 10(12) cm(-2) is still quite high and should be reduced. Density of slow surface states, being responsible for hysteresis of C-V characteristics, is much lower in case of plasma oxide, with C-V curves showing near-ideal high-frequency behavior.

Initial stages of HgCdTe oxidation in a glow discharge plasma in O2 atmosphere are first studied using the XPS method. The chemical composition of the growing native oxide layer is investigated and the oxidation kinetics is revealed. It is experimentally established that the mechanism of HgCdTe oxidation changes as the oxide thickness reaches 2-3 nm due to the change of the limiting stage of the chemical reaction. The composition of the formed oxide is varies with depth and is characterized by low mercury content. It is suggested that the diffusion of oxygen to the oxide–semiconductor interface and its predominant interaction with tellurium are the main mechanism of the native MCT oxide growth, so that the oxide region bordering the substrate is ∼10% oxygen depleted. The obtained results are discussed and compared with previously reported data on MCT oxidation in RF plasma and in liquid electrolytes.

In this paper, studies of the surface conductivity of thin disordered carbon nanotubes (CNTs) films, containing nanotubes of both metallic and semiconductor conductivity, are presented. The current-voltage (I-V) characteristics were obtained on the sensor type structures with circular interdigitated electrodes and the distance between the electrodes of 10, 20, 30 and 40 microns. The measurements were carried out under normal conditions as well as during adsorption and desorption of NH 3 , C 2 H 5 OH, and other vapors. The results can be used for development of multicomponent sensor devices to increase selectivity and sensitivity of an "electronic nose".

Metal-insulator-semiconductor (MIS) structures were fabricated on n-type variband HgCdTe with Al2O3 deposited by plasma-enhanced ALD. Early stages of the deposition process performed at 120 degrees C were studied by means of XPS for the first time. Partial decomposition and conversion of HgCdTe native oxide presented on the surface were observed as well as mercury atoms out-diffusion from the near-surface region. The width of alumina band gap and the offsets of Al2O3/HgCdTe bands were determined. Capacitance-voltage characteristics reveal a negative fixed charge with the density of similar to 1 x 10(12) cm(-2) and wide hysteresis depending on the voltage sweep range. An additional intermediate layer lowering an apparent permittivity value of the MIS insulator layer is found. By varying the thickness of the insulator of the samples, the permittivity of Al2O3 was extracted to be 7.6. The estimated Al2O3 properties correspond to the oxygen-deficient amorphous phase of alumina.

In this work the features of current transport through a barrier in Au/native fluoride/HgCdTe Schottky diode are under studying. Using I-V dependences at different (from 90 to 290 K) temperatures, it has been observed that an ideality factor decreases and a barrier height increases with a temperature increase what is in disagreement with the ideal thermionic emission theory of a Schottky barrier. The phenomenon assumed to be accounted for lateral non-uniformity of barrier heights at the metal/semiconductor interface. The Gaussian distribution is used to describe this inhomogeneity. Analysis of temperature I-V dependences allow us to conclude the double Gaussian distribution with the mean barrier heights of 0.5 eV and 0.67 eV and with the dispersions of 4.5 mV and 8.5 mV in 90-130 K and 130-270 K temperature ranges, respectively. With the Gaussian distribution taken into account, the Richardson constant value of 2 A/cm 2 K 2 which is close to the theoretical one has been determined from I-V measurements.

The work is aimed to studying a possibility of CdHgTe surface passivation and stabilization by tunnel-thin (∼ 2 nm) native oxide formed by glow discharge plasma oxidation. Kinetics of MCT plasma treatment in two regimes has been obtained. Investigation of the stabilization effect during vacuum annealing and platinum deposition has been performed. It has been established that presence of a native oxide layer on MCT surface results in elimination of mercury out diffusion during the processes. MIS structures with platinum contacts and thin native oxide have been made. They have rectifying behaviour in contrast with structures without the native oxide layer. The barrier height and the detectivity have been determined from the capacitance-voltage and current-voltage dependences. The detectivity value of 4×1011cm.Hz1/2W-1 (at 78 K) determined by dark current shot noise has been reached. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)