Superlattice (SL) phase change materials have shown promise to reduce the switching current and resistance drift of phase change memory (PCM). However, the effects of internal SL interfaces and intermixing on PCM performance remain unexplored, although these are essential to understand and ensure reliable memory operation. Here, using nanometer-thin layers of Ge2Sb2Te5 and Sb2Te3 in SL-PCM, we uncover that both switching current density (Jreset) and resistance drift coefficient (v) decrease as the SL period thickness is reduced (i.e., higher interface density); however, interface intermixing within the SL increases both. The signatures of distinct versus intermixed interfaces also show up in transmission electron microscopy, X-ray diffraction, and thermal conductivity measurements of our SL films. Combining the lessons learned, we simultaneously achieve low Jreset ≈ 3-4 MA/cm2 and ultralow v ≈ 0.002 in mushroom-cell SL-PCM with ∼110 nm bottom contact diameter, thus advancing SL-PCM technology for high-density storage and neuromorphic applications.
We acknowledge the financial support from the Semiconductor Research Corporation, SRC (tasks 3004.001 and 2966.011) and from the member companies of the Stanford Non-Volatile Memory Technology Research Initiative (NMTRI). Part of this work was performed at the Stanford Nanofabrication Facility (SNF) and Stanford Nanofabrication Shared Facilities (SNSF) supported by National Science Foundation ECCS-2026822. I.-K.O. and B.W. were supported by research grants (NRF-2020M3F3A2A01082593 and NRF-2021R1A4A1033155) from National Research Foundation (NRF) funded by the Ministry of Science and ICT, Korea. A.I.K. and X.W. are thankful to James McVittie and Carsen Kline for the lab support and to Chris Neumann for the electrical measurement setup. A.I.K acknowledges support from Stanford Graduate Fellowship, C.P. from the Stanford DARE Doctoral Fellowship, X.W. from the Stanford Electrical Engineering Department Fellowship, and H.K. from the Kwanjeong Educational Foundation Fellowship.
