Thermoelectric effects on phase change memory elements are computationally analyzed through 2-D rotationally symmetric finite-element simulations of reset operation on a Ge₂Sb₂Te₅ (GST) mushroom cell with 10-nm critical dimension. Temperature-dependent material parameters are used to determine the thermoelectric contributions at the junctions (Peltier heat) and within GST (Thomson heat). Thermal boundary resistances at the GST interfaces enhance the Peltier heat contribution. Peak current densities and thermal gradients are in the order of 250 MA/cm² and 50 K/nm. Overall, thermoelectric effects are shown to introduce significant voltage polarity dependence on the operation dynamics, peak temperatures, thermal gradients, volume of the molten region, energy required, and resistance contrast. Resistance contrasts of ~ 8.8 × 10³ were realized with 155 μA for the positive polarity and 245 μA for the negative polarity.

Fabrication and characterization of a guided-mode resonance-based polarizer is presented. This polarizer is made by electron-beam patterning a single layer of amorphous silicon on a glass substrate. The fabricated device has high and low transmittance for transverse-electric and transverse-magnetic polarizations, respectively, over a ~ 40-nm wavelength range for normally incident light. Its experimental extinction ratio is ~ 97:1 at a central wavelength of 1510 nm.

Phase-change memory (PCM) devices are enabled by amorphization- and crystallization-induced changes in the devices' electrical resistances. Amorphization is achieved by melting and quenching the active volume using short duration electrical pulses (∼ns). The crystallization (set) pulse duration, however, is much longer and depends on the cell temperature reached during the pulse. Hence, the temperature-dependent crystallization process of the phase-change materials at the device level has to be well characterized to achieve fast PCM operations. A main challenge is determining the cell temperature during crystallization. Here, we report extraction of the temperature distribution on a lateral PCM cell during a set pulse using measured voltage-current characteristics and thermal modelling. The effect of the thermal properties of materials on the extracted cell temperature is also studied, and a better cell design is proposed for more accurate temperature extraction. The demonstrated study provides promising results for characterization of the temperature-dependent crystallization process within a cell.

During the fast switching in Ge₂Sb₂Te₅ phase change memory devices, both the amorphous and fcc crystalline phases remain metastable beyond the fcc and hexagonal transition temperatures respectively. In this work, the metastable electrical properties together with crystallization times and resistance drift behaviour of GST are studied using a high-speed, device-level characterization technique in the temperature range of 300 K to 675 K.

Phase-change memory elements with 25-nm Ge₂Sb₂Te₅ thickness and 25-nm heater diameter with ±2-nm protrusion/recess of the heater are studied using 2-D finite-element simulations with rotational symmetry. Temperature-dependent material parameters are used to solve current continuity and heat equations self-consistently. Melting is accounted for by including latent heat of fusion in heat capacity at melting temperature. Electrical breakdown is modeled using additional field-dependent conductivity terms to enable set simulations. Analyses on current, voltage, energy, power, and minimum pitch requirements are summarized for reset/set operations with 1-ns/20-ns voltage pulses leading to ~500× difference between the reset and set resistance states.