Cyclotron resonance photoconductivity of a two-dimensional electron gas in HgTe quantum wells

Far-infrared cyclotron resonance photoconductivity (CRP) is investigated in HgTe quantum wells (QWs) of various widths grown on (013) oriented GaAs substrates. It is shown that CRP is caused by the heating of two-dimensional electron gas (2DEG). From the resonance magnetic field strength effective masses and their dependence on the carrier concentration is obtained. We found that the effective mass in each sample slightly increases from the value (0.0260 \pm 0.0005)m_0 at N_s = 2.2x10^11 cm^(-2) to (0.0335 \pm 0.0005)m_0 at N_s = 9.6x10^11 cm^(-2). Compared to determination of effective masses by the temperature dependence of magnitudes of the Shubnikov-de Haas (SdH) oscillations used so far in this material our measurements demonstrate that the CRP provides a more accurate (about few percents) tool. Combining optical methods with transport measurements we found that the transport time substantially exceeds the cyclotron resonance lifetime as well as the quantum lifetime which is the shortest.Comment: 3 pages, 2 figure

Influence of pulsed nanosecond volume discharge in atmospheric-pressure air on the electrical characteristics of MCT epitaxial films

The purpose of this paper was investigating the effect of volume nanosecond discharge in air at atmospheric pressure on the electro-physical properties of the HgCdTe (MCT) epitaxial films grown by molecular beam epitaxy. Hall measurements of electro-physical parameters of MCT samples after irradiation have shown that there is a layer of epitaxial films exhibiting n-type conductivity that is formed in the near-surface area. After more than 600 pulses of influence parameters and thickness of the resulting n-layer is such that the measured field dependence of Hall coefficient corresponds to the material of n-type conductivity. Also it is shown that the impact of the discharge leads to significant changes in electro-physical characteristics of MIS structures. This fact is demonstrated by increase in density of positive fixed charge, change in the hysteresis type of the capacitance-voltage characteristic, an increase in density of surface states. The preliminary results show that it is possible to use such actions in the development of technologies of the controlled change in the properties of MCT. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Admittance investigation of MIS structures with GgTe-based single quantum wells

This work presents results of the investigation of admittance of metal-insulator-semiconductor structure based on Hg1 − xCdxTe grown by molecular beam epitaxy. The structure contains a single quantum well Hg0.35Cd0.65Te/HgTe/Hg0.35Cd0.65Te with thickness of 5.6 nm in the sub-surface layer of the semiconductor. Both the conductance-voltage and capacitance-voltage characteristics show strong oscillations when the metal-insulator-semiconductor (MIS) structure with a single quantum well based on HgTe is biased into the strong inversion mode. Also, oscillations on the voltage dependencies of differential resistance of the space charge region were observed. These oscillations were related to the recharging of quantum levels in HgTe

Admittance of MIS structures based on graded-gap MBE HgCdTe with Al2O3 insulator

The paper presents the results of studies of the admittance of MIS structures based on heteroepitaxial MBE n (p)-Hg0.78Cd0.22Te with insulator coating SiO2/Si3N4 and Al2O3 in the test signal frequency range 10 kHz-1 MHz at temperatures ranging from 8 to 220 K. The main parameters of MIS structures with different insulators were determined. MIS structures with Al2O3 have a large enough insulator capacitance (compared to SiO2/Si3N4), a significant modulation capacitance on the CV characteristics, high dielectric strength and low values of the flat-band voltage. The effective charge density found from the value of the flat-band voltage and slow interface trap density for structures with Al2O3 comparable with the corresponding densities for structures with SiO2/Si3N4

Unipolar barrier structures based on HgCdTe for infrared detection

One of the topical areas of solid state photoelectronics is the creation of infrared detectors based on unipolar barrier systems (for example, with an nBn architecture). The greatest progress has been achieved in the development of barrier detectors based on semiconductors of the AIIIBV group, which is associated with the possibility of realizing systems with a zero barrier in the valence band. Unipolar barrier detectors based on mercury cadmium telluride (HgCdTe) grown by molecular beam epitaxy (MBE) are of interest due to significant technological advantages, since the creation of such devices can abandon the defect forming procedure of ion implantation. Despite a significant number of theoretical works, only a few attempts are known to practically implement nBn detectors based on MBE HgCdTe

Impact of the graded-gap layer on the admittance of MIS structures based on MBE-grown n-Hg1-xCdxTe (x = 0.22-0.23) with the Al2O3 insulator

The impact of the presence of the near-surface graded-gap layers with an increased content of CdTe on the admittance of MIS structures based on MBE-grown n-Hg1–xCdxTe (x = 0.22–0.23) with the Al2O3 insulating coating has been experimentally studied. It has been shown that the structures with a gradedgap layer are characterized by a deeper and wider capacitance dip in the low-frequency capacitance–voltage (CV) characteristic and by higher values of the differential resistance of the space-charge region than the structures without such a layer. It has been found that the main features of the hysteresis of capacitance dependences typical of the graded-gap structures with SiO2/Si3N4 are also characteristic of the MIS structures with the Al2O3 insulator. The factors that cause an increase in the CV characteristic hysteresis upon formation of the graded-gap layer in structures with SiO2/Si3N4 or Al2O3 are still debatable, although it may be assumed that oxygen plays a certain role in formation of this hysteresis

AlGaAs/GaAs Quantum Well Infrared Photodetectors

In this article, we present an overview of a focal plane array (FPA) with 640 × 512 pixels based on the AlGaAs quantum well infrared photodetector (QWIP). The physical principles of the QWIP operation and their parameters for the spectral range of 8–10 μm have been discussed. The technology of the manufacturing FPA based on the QWIP structures with the pixels 384 × 288 and 640 × 512 has been demonstrated. The parameters of the manufactured 640 × 512 FPA with a step of 20 μm have been given. At the operating temperature of 72 K, the temperature resolution of QWIP focal plane arrays is less than 35 mK. The number of defective elements in the matrix does not exceed 0.5%. The stability and uniformity of the FPA have been demonstrated

An experimental study of the dynamic resistance in surface leakage limited nBn structures based on HgCdTe grown by molecular beam epitaxy

Mid-wave infrared nBn structures based on HgCdTe grown by molecular beam epitaxy on GaAs (013) substrates were fabricated. The composition in the absorbing layer was 0.29, and in the barrier layer it was 0.67. It was shown that the dark currents of the created nBn structures are limited by the surface leakage component. To study the bulk component of the dark current, it was proposed to use the admittance measurements of test metal-insulator-semiconductor (MIS) devices based on fabricated nBn structures in the case of the formation of a backward contact to the absorbing layer. It was established that surface leakage does not afect the dynamic resistance of the MIS device barrier. The dependence of the dynamic resistance of the barrier layer (Rb) of the MIS device in the accumulation mode on the area of the front electrode (A), voltage, and temperature was determined. It was shown that, with the exclusion of surface leakage, the values of the RbA product in a temperature range of 230–300 K at forward biases are determined by the difusion current of holes from the contact layer, and at reverse biases, by the difusion current from the absorbing layer. It was found that at temperatures of 210–300 K, RbA values exceeding the values of this parameter determined according to the empirical model Rule 07 were realized in the fabricated structures