Multiple phase-transition in Ge2Sb2Te5 based phase change memory cell by current–voltage measurement

A Ge2Sb2Te5 based phase change memory (PCM) cell was fabricated by a standard 0.18 μm complementary metal–oxide-semiconductor technology, combined with subsequent special lift-off process. Through current–voltage measurements, the phase change from the amorphous state (high resistance state) to the face-centered cubic crystalline state and the hexagonal close-packed crystalline state (two kinds of different low resistance states) was observed. In addition to the typical phase-transition, where the PCM cell changes from initial amorphous state directly into final crystalline state, intermediate resistance states were observed during the phase changes from the high resistance state to the low resistance state.