Abstract
This work introduces the atomic layer deposition (ALD) of Sn-doped GeSe2 (SnGS2) films for developing arsenic-free Ovonic threshold switch (OTS) devices with low off-current (Ioff) and desirable threshold voltage (Vt). The undoped GeSe2 film exhibits high Vt and low endurance characteristics despite its low Ioff originating from a large mobility gap. Such problems could be overcome by appropriate doping, and thus, Sn was doped into the GeSe2 film using a supercycle consisting of SnNx and GeSe2 subcycles. The co-injection of NH3 with Se-precursor ([(CH3)3Si]2Se) during the GeSe2 subcycle generated a reactive H2Se intermediate, which enhanced the reactivity and transformed the pre-deposited SnNx to SnSe2. The overall cation-to-anion ratio of the deposited films remained at approximately 1 : 2, with amorphous structure and smooth surface morphology. The planar OTS device using SnGS2 films with a Sn concentration of 9.6%, for which the crystallization temperature was >400 °C, showed the lowest Vt of ∼3.5 V and Ioff of ∼12.5 nA at half Vt and demonstrated switching endurance over 106 cycles. Furthermore, a vertical-type OTS device was fabricated using the same SnGS2 film using the excellent step coverage of ALD, exhibiting similar switching characteristics to its planar counterpart.
Published Version
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