Space Charge Limited Current Research Articles

Effect of space charge limited current on performance of organic field-effect transistors

The crucial parameter that determines the performance of a semiconductor material in organic field-effect transistors (OFETs) is the charge carrier mobility. The conventional method of its determination based on Shockley’s equations can lead to incorrect mobility evaluation due to contact effects. Particularly, in the common staggered OFET architecture (top-contact bottom-gate or bottom-contact top-gate), the space-charge limited current (SCLC) effect in the active layer under/above the source and drain contacts decreases the source-drain current. In this work, we model the effect of SCLC under/above the source and drain electrodes on the OFET apparent mobility (i.e., calculated from the device characteristics) and apparent threshold voltage for different active layer thickness and intrinsic mobility anisotropy. For the saturation regime, we derived simple analytical expressions for transfer characteristics and apparent mobility. Our modeling shows that the apparent OFET mobility is more than five times lower than the intrinsic one for the active layer thicker than 100 nm with mobility anisotropy (along vs across the active layer) higher than 100. While the SCLC effect does not change the apparent threshold voltage, it reveals itself as a kink at near zero voltage in the output characteristics. The proposed model gives analytical expressions for the transfer characteristics and apparent mobility as explicit functions of the intrinsic mobility and the device parameters in the saturation regime and as implicit functions in the linear regime. Our findings provide guidelines for accurate evaluation of the intrinsic mobility in OFETs fabricated in the staggered architecture and for further improvement of OFET performance.

An Organic Bipolar Resistive Switching Memory Device Based on Natural Melanin Synthesized From Aeromonas sp. SNS

A Ag/melanin/SS memristive device with remarkably good endurance and retention properties is demonstrated using natural melanin isolated from bacterium Aeromonas sp. SNS. Purified and characterized melanin is used for the development of a non‐volatile memory device. The device is operated under electroforming‐free mode and requires only ±0.6 V resistive switching voltage. 2 × 104 switching cycles endurance is achieved with an approximately 10X memory window at 0.2 V read voltage. In addition to this, the low resistance state (LRS) and high resistance state (HRS) are stable over 103 s without any observable degradation in the resistance states. Standard deviation and coefficient of variation of LRS and HRS are very small compared to other memory devices reported in the literature. Furthermore, the Ag/melanin/SS memristive device shows rich nonlinear behavior and possesses negative differential resistance effect during positive bias. Charge transportation in the device is due to the ohmic and space charge limited current. The formation and breaking of the conductive filament are responsible for the bipolar resistive switching effect due to hybrid electronic‐ionic charge transportation. Rich I–V characteristics, very low switching voltage, and remarkable nonvolatile memory performance make melanin a strong candidate for next generation organic non‐volatile memory devices.

Improved resistive switching performance in Cu-cation migrated MoS2 based ReRAM device incorporated with tungsten nitride bottom electrode

The resistive switching characteristics of sputtered deposited molybdenum disulphide (MoS2) thin film has been investigated in Cu/MoS2/W2N stack configuration for Resistive Random Access Memory (ReRAM) application. The benefits of incorporating tungsten nitride (W2N) as a bottom electrode material were demonstrate by stability in operating voltages, good endurance (103 cycles) and long non-volatile retention (103 s) characteristics. Resistive switching properties in Cu/MoS2/W2N structure are induced by the formation/disruption of Cu conducting filaments in MoS2 thin film. Ohmic law and space charge limited current (SCLC) are observed as dominant conduction mechanism in low resistance state (LRS) and high resistance state (HRS) respectively. This study suggests the application of MoS2 thin films with W2N bottom electrode for next generation non-volatile ReRAM application.

Field Effect in PbSnTe:In Films with Low Conductivity in the Mode of Injection from Contacts and Space-Charge Limitation of the Current

At T = 4.2 K, a strong change (up to 4 times) in the space-charge-limited current (SCLC) is observed for the first time at samples based on semi-insulating PbSnTe:In films grown by molecular-beam epitaxy on BaF2(111) substrates. The obtained results agree with experiments on the effect of treatment of the surface of PbSnTe:In films on the space-charge-limited current with a variation in the current to 103 times or more. At a qualitative level, the model is considered which assumes the substantial contribution of localized surface states to space charge formed in the mode of space-charge-limited current due to the injection of charge carriers from contacts.

Electrical transport phenomena in nanostructured porous-silicon films

The charge transport mechanisms in nanostructured porous silicon (PS) films were studied through current-voltage (I-V) measurements of planar Au/PS/Au structures at 300 K. The films were formed by electrochemical etching of 1-5 Ω-cm p-type Si (100) wafers producing PS layers of 4.48 x 109 Ω-cm. The charge transport is limited both by the space charge limited currents (SCLC) and the carrier trapping-detrapping kinetics in the inherent localized PS energy levels. I-V characteristics evolve according to the trapping-detrapping carrier kinetics in the PS films showing that the electrical current can be controlled by applying external electric fields. An equivalent trap filling limiting voltage (VTFL) was identified that shifts between 1 and 3 volts by the carrier trapping-detrapping kinetics from the PS intrinsic defect states. An energy band diagram for the PS films is schematically depicted including the influence of the intrinsic PS defect states. To give a reasonable explanation of the found behavior the existence of a thin silicon oxide film covering the network-like-silicon-nanocrystallites is required, in agreement with the widely accepted PS structural models.

Electrochemically induced charge injection in disordered organic conductive polymers

This paper deals with the electrochemically induced charge injection in the conductive polymer (CP), exemplified by well examined archetypal CP—poly(3-hexylthiophene-2,5-diyl). The polar solvent of acetonitrile with salt tetrabutylammonium hexafluorophosphate was used to transport electrons in the electrolyte. The decisive mechanism is the recombination current at the electrolyte/CP interface taking place at the Fermi energy of CP, whose energy position is determined by the externally applied voltage. The corresponding mechanism of the charge carrier transport in the polymer bulk is the space-charge limited current (SCLC) by holes or electrons (or more precisely positive and negative polarons) at the respective transport paths of HOMO and LUMO bands. The charge transport mechanisms and the occupation statistics are the basis of the energy-resolved electrochemical impedance spectroscopy for the mapping of the density of electronic states of conductive organic semiconductors [F. Schauer, V. Nádaždy, and K. Gmucová, J. Appl. Phys. 123, 161590 (2018)]. From the application point of view, the major message of the paper is that it is possible to pass high current densities of the order of 0.1 A cm−2 via electrochemical systems with the CP, induced by means of doping processes of both CP surface and its bulk, leading to the charge injection and SCLC in CP.

Non-volatile resistive switching in oxide ion conductor BiYO3 thin films

We experimentally demonstrate non-volatile resistive switching (RS) with a resistance window of ∼10× in oxide ion conductor BiYO3 (BYO) thin films. (111)-oriented BYO films of multiple thicknesses (20 nm–300 nm) were deposited using the pulsed laser deposition technique on a Pt/TiO2/SiO2/Si substrate. The thermal stability of BYO films in a wide temperature range (10 K–800 K) was confirmed, using temperature dependent dielectric measurements. Further, impedance spectroscopy suggests the presence of oxygen vacancies (defects) at the Au/BYO interface in the high resistance state (after forming) too. Root mean square roughness of the films varied from 1.16 nm to 2.76 nm, confirming a uniform and homogeneous surface. We explain the conduction mechanism in our Au/BYO/Pt devices using space charge limited current (SCLC) and Ohmic conduction models. The bipolar RS characteristics of the BYO devices are empirically modeled on the basis of the oxygen ion driven filamentary switching process.

Conduction mechanisms in lanthanum manganite nanofibers

Lanthanum manganites are being constantly investigated for their interesting magnetic and transport properties. In this study, polycrystalline, single phase lanthanum manganite (LaMnO3) nanofibers were synthesized using an electrospinning technique, and characterized in terms of phase, microstructure, ac and dc electrical properties. X-ray diffraction and scanning electron microscopy revealed the formation of uniform composite nanofibers (average dia.∼ 600 nm) at 100 °C and polycrystalline single phase porous LaMnO3 nanofibers (average dia.∼ 400 nm) when calcined at 600 °C. Temperature dependent impedance and current-voltage (IV) characteristics of LaMnO3 nanofibers deposited on an interdigitated electrode type device, were investigated at temperatures ranging from 298 to 378 K. The observed decrease in the dielectric constant at high frequencies may be due to decrease in the contribution from dipolar polarization. Analysis of ac conductivity indicated thermally activated type conduction mechanism in these nanofibers which could be explained by a correlated barrier hopping (CBH) model. The observed decreasing trend in activation energy with increasing frequency also supported the CBH model. Furthermore, the analysis of log (J) vs. E0.5 curves at different temperatures showed a large difference of ~5.82 between the experimental and theoretical field lowering coefficient with an internal field enhancement factor of α2 = 33.91. This result excluded the possibility of Pool-Frenkel type conduction and the observed variation might be due to the presence of some localized electric fields. Further investigation of IV characteristics revealed that the ‘space-charge-limited current (SCLC) with traps’ may be the possible conduction mechanism.

Performance improvement of perovskite solar cells using electron and hole transport layers

In this study, various electron and hole transport structures were created in perovskite solar cells to ameliorate the problem of carrier mobility balance. Balanced electron and hole mobilities could reduce carrier recombination probability in the cells to improve their performance. The space-charge-limited current (SCLC) method was used to calculate the electron and hole mobilities of perovskite devices with various electron transport layers (ETLs) and hole transport layers (HTLs). Compared with perovskite devices with [6,6]-phenyl-C-61-butyric acid methyl ester (PC60BM) single ETL and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) single HTL, the current density and power-conversion efficiency of perovskite solar cells with [6,6]-phenyl-C-71-butyric acid methyl ester/pristine fullerenes (PC70BM/C70) dual ETLs and PEDOT:PSS/poly[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]-thiophenediyl] (PTB7) dual HTLs increased from 18.22 to 24.11 mA/cm2 and 7.07% to 14.11%, respectively. Compared with the carrier mobility balance ratio (μh/μe) of 0.35 of perovskite solar cells with PC60BM single ETL and PEDOT:PSS single HTL, perovskite solar cells with dual ETLs and dual HTLs showed a μh/μe of 0.90, which led to the performance improvement of the cells.

Converging the Hole Mobility of Poly(2-N-carbazoylethyl acrylate) with Conjugated Polymers by Tuning Isotacticity

Nonconjugated electroactive polymers (also known as pendant or side-chain electroactive polymers) promise several potential advantages relative to conjugated polymers including enhanced mechanical durability, greater stability and synthesis via living polymerization techniques. However, most previous examples suffer from low charge carrier mobility. Here, using poly(2-N-carbazoylethyl acrylate) (PCzEA) as a model polymer, we investigate the ability of side-chain tacticity to influence hole mobility. Specifically, we investigated polymers with dyad isotacticity (m) ranging from ∼45 to ∼95% synthesized by several methods including free radical polymerization and anionic polymerization. We found that the hole mobility (μh) measured via the space charge limited current (SCLC) technique increased proportionally to the increasing isotacticity from 2.11 × 10-6 cm2 V-1 s-1 (m = 45.5%) to 4.68 × 10-5 cm2 V-1 s-1 (m = 94.7%) in unannealed samples and that mobilities could be boosted as high as 2.74 × 10-4 cm2 V-1 s-1 (m = 94.7%) with thermal annealing, which rivaled the well-known conjugated polymer poly(3-hexylthiophene) (P3HT) (μh = 5.8 × 10-4 cm2 V-1 s-1). As such, we report here clear experimental evidence that control of side chain tacticity can enhance charge carrier mobility in nonconjugated pendant electroactive polymers, converging with mobilities typically only observed in conjugated polymers.

Influence of Systematic Incorporation of Conjugation-Break Spacers into Semi-Random Polymers on Mechanical and Electronic Properties.

An extensive family of semi-random polymers was prepared via Stille polycondensation with varying contents of alkyl spacers incorporated into the polymer backbone to serve as a break in conjugation. This family was investigated to determine the effect of alkyl spacer length and percent incorporation on the optical, electronic, and mechanical properties. The optical bandgap was found to steadily increase from 1.53 to 1.70 eV as the amount of spacer was increased from 10 mol percent to 40 mol percent while the length of the spacer had little to no effect. In space charge limited current (SCLC) carrier mobility measurements, hole mobility was found to decrease as the amount of spacer increased but was found to steadily increase as the length of the spacer was increased from 6 to 10 carbons. Mechanical properties were observed by film-on-elastomer and film-on-water measurements, with low elastic moduli and high ductility attributed both to the break in conjugation as well as the semi-random structure of the polymer backbone. Measurements of the mechanical properties using the buckling method revealed elastic moduli between 0.14 and 1.3 GPa, and several polymers, when bonded to an elastomeric substrate, could be stretched beyond 80% strain. These polymers were further tested as free-standing films by obtaining a pull test on the surface of water, where we obtained tensile moduli between 0.13 and 0.75 GPa. These results indicate that semi-random polymers with conjugation-break spacers are promising candidates for further study in flexible electronics.

Nonstoichiometric Solution-Processed BaTiO₃ Film for Gate Insulator Applications.

Solution processed barium titanate (BTO) was used to fabricate an Al/BaTiO3/p-Si metal-insulator-semiconductor (MIS) structure, which was used as a gate insulator. Changes in the electrical characteristics of the film were investigated as a function of the film thickness and post deposition annealing conditions. Our results showed that a thickness of 5 layers and an annealing temperature of 650 °C produced the highest electrical performance. BaxTi1-xO3 was altered at x = 0.10, 0.30, 0.50, 0.70, 0.90, and 1.0 to investigate changes in the electrical properties as a function of composition. The highest dielectric constant of 87 was obtained for x = 0.10, while the leakage current density was suppressed as Ba content increased. The lowest leakage current density was 1.34×10-10 A/cm2, which was observed at x = 0.90. The leakage current was related to the resistivity of the film, the interface states, and grain densification. Space charge limited current (SCLC) was the dominant leakage mechanism in BTO films based on leakage current analysis. Although a Ba content of x = 0.90 had the highest trap density, the traps were mainly composed of Ti-vacancies, which acted as strong electron traps and affected the film resistivity. A secondary phase, Ba2TiO4, which was observed in cases of excess Ba, acted as a grain refiner and provided faster densification of the film during the thermal process. The absence of a secondary phase in BaO (x = 1.0) led to the formation of many interface states and degradation in the electrical properties. Overall, the insulator properties of BTO were improved when the composition ratio was x = 0.90.

Charge carrier transport and electroluminescence in atomic layer deposited poly-GaN/c-Si heterojunction diodes

In this work, we study the charge carrier transport and electroluminescence (EL) in thin-film polycrystalline (poly-) GaN/c-Si heterojunction diodes realized using a plasma enhanced atomic layer deposition process. The fabricated poly-GaN/p-Si diode with a native oxide at the interface showed a rectifying behavior (Ion/Ioff ratio ∼ 103 at ±3 V) with current-voltage characteristics reaching an ideality factor n of ∼5.17. The areal (Ja) and peripheral (Jp) components of the current density were extracted, and their temperature dependencies were studied. The space charge limited current (SCLC) in the presence of traps is identified as the dominant carrier transport mechanism for Ja in forward bias. An effective trap density of 4.6 × 1017/cm3 at a trap energy level of 0.13 eV below the GaN conduction band minimum was estimated by analyzing Ja. Other basic electrical properties of the material such as the free carrier concentration, effective density of states in the conduction band, electron mobility, and dielectric relaxation time were also determined from the current-voltage analysis in the SCLC regime. Further, infrared EL corresponding to the Si bandgap was observed from the fabricated diodes. The observed EL intensity from the GaN/p-Si heterojunction diode is ∼3 orders of magnitude higher as compared to the conventional Si only counterpart. The enhanced infrared light emission is attributed to the improved injector efficiency of the GaN/Si diode because of the wide bandgap of the poly-GaN layer and the resulting band discontinuity at the GaN/Si interface.

Performance analysis of Fe-doped calcium copper titanate quadruple perovskite in optoelectronic device

We report here the synthesis of nanosized (50–55 nm) Fe-doped calcium copper titanate CaCu2.5Ti3.5FeO12 quadruple perovskite semiconductor by a two-step synthetic protocol involving citrate combustion for precursor synthesis followed by its calcination at different temperatures for the synthesis of the target materials. Materials were applied in thin film metal-semiconductor (MS) junction based Schottky Barrier Diodes (SBDs). The non-linear current-voltage characteristics indicate successful application of the materials in optoelectronic device. The device performance of the fabricated SBDs are analyzed by employing the thermionic emission (TE) theory and the space charge limited current (SCLC) theory followed by a schematic band structure.

Thickness Dependence of Space-Charge-Limited Current in Spatially Disordered Organic Semiconductors

Charge transport properties in organic semiconductors are determined by two kinds of microscopic disorders, namely, energetic disorder related to the distribution of localized states and the spatial disorder related to the morphological features of the material. From a semiclassical picture, the charge transport properties are crucially determined by both the carrier mobility and the electrostatic field distribution in the material. Although the effect of disorders on carrier mobility has been widely studied, how electrostatic field distribution is distorted by the presence of disorders and its effect on charge transport remain unanswered. In this paper, we present a modified space-charge-limited current (SCLC) model for spatially disordered organic semiconductors based on the fractional-dimensional electrostatic framework. We show that the thickness dependence of the SCLC is related to the spatial disorder in organic semiconductors. For trap-free transport, the SCLC exhibits a modified thickness scaling of J α L <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3α</sup> , where the fractional-dimensional parameter α accounts for the spatial disorder in organic semiconductors. The trap-limited and field-dependent mobility are also shown to obey an α-dependent thickness scaling. The modified SCLC model shows good agreement with several experiments on spatially disordered organic semiconductors. By applying this model to the experimental data, the standard charge transport parameters can be deduced with better accuracy than by using existing models.

Influence of Substrate Modification with Dipole Monolayers on the Electrical Characteristics of Short-Channel Polymer Field-Effect Transistors

This study investigates the influence of self-assembled monolayer treatment of gate insulators on the electrical characteristics of bottom-gate/bottom-contact organic field-effect transistors (OFETs) with short channel lengths of 5 μm to 30 nm. The treatment of 3-chloropropyltrichlorosilane (CPTS) with large dipoles produces a high built-in electric field perpendicular to the SiO2 gate insulator surface, which results in a threshold voltage shift and enhanced hole injection compared to the treatment of phenethyltrichlorosilane (PETS) with small dipoles. Pronounced parabolic drain current‒voltage (ID‒VD) characteristics due to a space-charge limited current are observed in short-channel OFETs based on poly(3-hexylthiophene) with CPTS-treated gate insulators. CPTS treatment on short-channel OFETs based on poly(9,9-dioctylfluorene-co-bithiophene) (F8T2) suppresses the nonlinear ID increase in the low VD region caused by the voltage drop at the Au/F8T2 contact. The influence of the increase in the net source-drain electric field associated with the reduced voltage drops on the channel-length dependence of the field-effect mobility of short-channel F8T2 FETs is also discussed.

Forward and reverse bias current–voltage (I–V) characteristics in the metal–ferroelectric–semiconductor (Au/SrTiO3/n-Si) structures at room temperature

The main electrical parameters of fabricated Au/SrTiO3/n-Si (MFS) structures have been investigated by using various methods. The values of ideality factor (n) and zero-bias barrier height (ΦB0) are calculated from the forward bias current–voltage (IF–VF) data as 0.60, and 0.48 eV from thermionic theory (TE) and Cheung functions, respectively. The value of Rs is also obtained from the Norde function and Cheung functions as 87.83 and 137.57 Ω, respectively. The discrepancy between these results can be attributed to the calculated method and the measured voltage range. Besides, the energy density distribution profile of interface state (Nss) was obtained from the (IF–VF) data by taking into account voltage dependent barrier height (BH), n and without Rs. On the other hand, the possible current conduction mechanism (CCM) are determined by utilizing the In(IF) versus In(VF) and In(IR) versus VR1/2 plots. The double logarithmic IF–VF plot shows three linear regions which are corresponding to low, moderate and high bias voltages with different slopes (m) as 2.40, 1.96 and 1.27 respectively. While the first region space charge limited current (SCLC) is dominated, the other two regions ohmic behavior is dominated. The field-lowering coefficient (β) was also obtained from the slope of In(IR)–V1/2 plot as 4.40 $$\times$$ 10−6 eV−1 m1/2 V1/2. This value of β is close to theoretical value of Poole–Frenkel emission (PFE) rather than Schottky emission (SE) mechanism.

Interface-Induced Face-on Orientation of Organic Semiconductors with a Template Layer and Its Application to Vertical-Type Organic Transistors

Molecular orientation to the substrate surface is a fundamental problem in organic semiconductor devices due to the anisotropic nature of optoelectronic properties of organic semiconductors. A face-on molecular orientation with the molecular planes parallel to the substrate, is ideal for out-of-plane charge carrier transport for vertical-type organic transistors where charge carriers flow perpendicularly to the substrate. It is usually difficult to induce the face-on molecular orientation on the substrate where intermolecular interactions are stronger than the molecule–substrate surface interactions. Most of the organic semiconductor materials show an edge-on orientation with the molecular planes vertical to the substrate, which is unsuitable for out-of-plane charge carrier transport. Template layer techniques have been proven to enhance the molecule–substrate surface interactions by inserting template materials between the substrate and organic layer. One of the template materials, perylene 3,4,8,9-tetracarboxylic dianhydride (PTCDA) exceptionally show the face-on orientation on the substrate and act as the template layer due to the π-π interactions between PTCDA and the upper side molecules. It has been known that PTCDA is effective for orientation control of phthalocyanine and its derivatives. However, it is still not clear about templating effect for other materials and vertical carrier transport property of organic semiconductors oriented with PTCDA. In this study, we investigated molecular orientation of various π-conjugated crystalline molecules on PTCDA, and the mechanism of orientation control from the crystal structure view point. We also measured the vertical carrier mobility of the oriented molecules and the performance of vertical-type organic transistors, and revealed the effect of orientation control for vertical carrier transport. Dimethyl-3,4,8,9-perylenedicarboximide (MePTC), copper-phthalocyanine (CuPc), dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT), pentacene, and diindenoperylene (DIP) were deposited on glass substrates by thermal vacuum evaporation after deposition of PTCDA. X-ray diffraction (XRD) measurements were carried out in the out-of-plane configuration to evaluate molecular orientation. In these organic semiconductor molecules, MePTC and CuPc on PTCDA gave a diffraction peak at 27.7° with d-spacing of 3.33 Å corresponding to the distance of π-π stacking, which indicates the face-on orientation of the molecules. DNTT, pentacene, and DIP had no diffraction peaks showing the face-on orientation. The difference of molecular orientation results from molecular packing in the crystal structure. Vertical carrier mobility of MePTC was measured by the space charge limited current (SCLC) technique. The electron mobility improved from 1.3×10-4 cm2/Vs to 4.3×10-4 cm2/Vs due to the face-on orientation control. The MePTC film oriented with PTCDA was applied to the metal base organic transisitor (MBOT) which is one of the vertical-type organic transistors, resulting in higher output current compared to the device without PTCDA.

Electrical characterization studies and doping effects of rubidium carbonate in organic layer by admittance spectroscopy

The doping effects and electrical characteristics of rubidium carbonate (Rb2CO3) in organic bipolar charge transport material 2-methyl-9,10-di(2-naphthyl) anthracene (MADN) has been investigated. Utilizing temperature-dependent admittance spectroscopy, the electron injection barrier (so-called activation energy) is verified to be reduced from 1.33 to 0.2878 eV by the incorporation of Rb2CO3 from 0 to 33 vol%. The precision of admittance spectroscopy is further proved by photovoltaic measurement. Higher mobility has achieved using space-charge-limited current (SCLC) determination. Consequently, these enhancements in electron injection and transport yield superior device performance for organic light-emitting diodes (OLEDs).

Performance Comparison of X- and &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$\gamma$ &lt;/tex-math&gt; &lt;/inline-formula&gt;-Ray CdTe Detectors With MoO&lt;italic&gt;x&lt;/italic&gt;, TiO&lt;italic&gt;x&lt;/italic&gt;, and TiN Schottky Contacts

Electrical characteristics of Mo–MoO x /p-CdTe/MoO x –Mo, Ti–TiO x /p-CdTe/MoO x –Mo, and Ti–TiN/p-CdTe/MoO x –Mo structures, manufactured by magnetron sputtering of the thin films on CdTe semi-insulating crystals, produced by Acrorad Co. Ltd. were studied. The optimization of conditions of the substrate pretreatment and the contacts deposition allowed to reduce the dark current of the Mo–MoO x /p-CdTe/MoO x –Mo detectors compared to earlier analogs and, consequently, to improve its spectrometric characteristics. Charge transport mechanisms in the structures under investigation were determined: the generation-recombination within the space-charge region at relatively low voltages and space charge limited currents at high voltages. There was shown that the structures Mo–MoO x /p-CdTe/MoO x –Mo, Ti–TiO x /p-CdTe/MoO x –Mo, and Ti–TiN/p-CdTe/MoO x –Mo can be used for practical applications in the X- and $\gamma $ -ray detectors.