Soret-Effect Induced Phase-Change in a Chromium Nitride Semiconductor Film

Phase-change materials such as Ge-Sb-Te (GST) exhibiting amorphous and crystalline phases can be used for phase-change random-access memory (PCRAM). GST-based PCRAM has been applied as a storage-class memory; however, its relatively low ON/OFF ratio and the large Joule heating energy required for the RESET process (amorphization) significantly limit the storage density. This study proposes a phase-change nitride, CrN, with a much wider programming window (ON/OFF ratio more than 10⁵) and lower RESET energy (one order of magnitude reduction from GST). High-resolution transmission electron microscopy revealed a phase-change from the low-resistance cubic CrN phase into the highly resistive hexagonal CrN₂ phase induced by the Soret-effect. The proposed phase-change nitride could greatly expand the scope of conventional phase-change chalcogenides and offer a strategy for the next-generation of PCRAM, enabling a large ON/OFF ratio (∼10⁵), low switching energy (∼100 pJ), and fast operation (∼30 ns).