Alexey Babich

Influence of indium doping on the electrical properties of Ge2Sb2Te5 thin films for nonvolatile phase change memory devices

In this article the influence of different amounts of In (0, 0.5, 1 and 3 wt. %) on the thermal and electrical properties of Ge2Sb2Te5 thin films for nonvolatile phase change memory devices is investigated. Crystallization temperature, resistivity, width of the optical band gap, Urbach energy, activation energy and type of conductivity are estimated for all investigated compounds. Storage and data processing times of the PCM cells on the basis of investigated materials were calculated. Nonmonotonic concentration dependences of properties were observed.

Integral isoconversional method for evaluating crystallization parameters of thin films of Ge2Sb2Te5 phase change memory materials

We propose a method for evaluating kinetic parameters for the crystallization of thin films of phase change materials. Its basic principle is to jointly use model-free and model isoconversional methods in analyzing differential scanning calorimetry results. Using this method, we have identified the reaction model and evaluated the activation energy for crystallization and pre-exponential factor as a function of the degree of conversion for Ge2Sb2Te5-based thin films.

Influence of Ti Doping on the Properties of Ge-Sb-Te Thin Films for Phase Change Memory

The influence of Ti doping on the resistivity, activation energy of conductivity, energy band gap, Urbach energy, crystallization temperature, heat effect and crystallization kinetic parameters in Ge2Sb2Te5 thin films for phase change memory was investigated. It was shown that introduction of Ti influences on the thermal properties, and kinetics of crystallization process. Results of analyzes showed that Ti doping affects crystallization time, and probability of spontaneous crystallization at room temperature, which must be taken into consideration at designing PCM cells with Ti electrodes.

Electrical Properties and Transport Mechanisms in Phase Change Memory Thin Films of Quasi-Binary-Line GeTe-Sb2Te3 Chalcogenide Semiconductors

The temperature dependences of the resistivity and current–voltage (I–V) characteristics of phase change memory thin films based on quasi-binary-line GeTe–Sb2Te3 chalcogenide semiconductors Ge2Sb2Te5, GeSb2Te5, and GeSb4Te7 are investigated. The effect of composition variation along the quasibinary line on the electrical properties and transport mechanisms of the thin films is studied. The existence of three ranges with different I–V characteristics is established. The position and concentration of energy levels controlling carrier transport are estimated. The results obtained show that the electrical properties of the thin films can significantly change during a shift along the quasi-binary line GeTe–Sb2Te3, which is important for targeted optimization of the phase change memory technology.

Investigation of the Crystallization Kinetics in the Phase Change Memory Materials of Ge–Sb–Te System

In this work mechanism and kinetics of crystallization for thin films on the basis of Ge–Sb–Te–Bi and Ge–Sb–Te–In perspective for phase change memory application were investigated. Possible data processing and storage times of the PCM cell were estimated. It was shown that PCM cell based on Ge2Sb2Te5 + 0.5 wt% Bi have minimum data processing and maximum data storage times in comparison with the other investigated materials.

Influence of doping on the crystallization kinetics of Ge-Sb-Te thin films for phase-change memory application

Crystallization kinetics in thin films of Ge2Sb2Te5 doped by Bi and Ti was studied. It has been shown that introduction of these impurities may have an impact on the kinetic parameters of the crystallization process. The possible recording and storage times of devices based on investigated materials were evaluated. It was shown that GST225 + 0,5 wt. % Bi has the best characteristics among the studied materials. Estimations showed that this composition can provide switching time of the phase-change memory cells less than 1 ns and it is extremely stable at room temperatures which is important for the reliable storage of information in memory cells.

Phase separation in chalcogenide semiconductors of the Ge-Te system upon thermal cycling

Close-to-eutectic compositions in the Ge-Te system are analyzed and their behavior with repeated heat treatments is studied by means of differential scanning calorimetry and X-ray diffraction. It is shown that repeated heat treatment of the compositions under study leads to phase separation in the material. Assumptions are made about the nature of processes occurring in the materials subjected to heat treatment.