High-performance MoS2 phototransistors with Hf1–x Al x O back-gate dielectric layer grown by plasma enhanced atomic layer deposition

Molybdenum sulfide (MoS₂) as an emerging optoelectronic material, shows great potential for phototransistors owing to its atomic thickness, adjustable band gap, and low cost. However, the phototransistors based on MoS₂have been shown to have some issues such as large gate leakage current, and interfacial scattering, resulting in suboptimal optoelectronic performance. Thus, Al-doped hafnium oxide (Hf_1-xAl_x) is proposed to be a dielectric layer of the MoS₂-based phototransistor to solve this problem because of the relatively higher crystallization temperature and dielectric constant. Here, a high-performance MoS₂phototransistor with Hf_1-xAl_xO gate dielectric layer grown by plasma-enhanced atomic layer deposition has been fabricated and studied. The results show that the phototransistor exhibits a high responsivity of 2.2 × 10⁴A W^-1, a large detectivity of 1.7 × 10¹⁷Jones, a great photo-to-dark current ratio of 2.2 × 10⁶%, and a high external quantum efficiency of 4.4 × 10⁶%. The energy band alignment and operating mechanism were further used to clarify the reason for the enhanced MoS₂phototransistor. The suggested MoS₂phototransistors could provide promising strategies in further optoelectronic applications.