講演情報
[18a-PA3-19]Low-Power GaS Phototransistors with Mist-CVD-Grown Al–Ti–O Gate Dielectrics
〇(PC)Abdul A Kuddus1, Tenryu Tamura1, Keiji Ueno2, Hajime Shirai3,2, Shinichiro Mouri1 (1.Ritsumeikan Univ., 2.Saitama Univ., 3.Kanagawa Univ.)
キーワード：
AlTiO、GaS、Phototransistor
Group III–VI two-dimensional (2D) gallium sulfide (GaS) is an emerging electronic and optoelectronic semiconductor which exhibits a wide bandgap (≈ 2.5–3.2 eV), enabling strong UV–visible absorption, high intrinsic responsivity, and excellent thermal stability. Despite these distinct properties, GaS field-effect transistors (FETs) fabricated on conventional SiO2 substrates reasonably suffer from low carrier mobility (≈ 0.1 cm2 V-1 s-1) due to Coulomb scattering, strong phonon coupling, and trap-induced threshold voltage shifts, resulting in slow photoresponse and limited device performance [1-4]. Although suspended GaS devices show high responsivity (≈103 AW-1), their fabrication complexity limits scalability [1]. Herein, we demonstrate few-layer GaS (~3.4 nm) phototransistors directly fabricated on high-κ AlOx/AlTiO (ATO; Al: Ti =77:23) gate dielectrics, providing an effective and scalable strategy to improve interface quality and overall device performance. The ~45 nm-thick Al0.77Ti0.23Oy films were deposited by mist CVD by Al(acac)3 and Ti(acac)2OiPr2 precursors, followed by an ultrathin AlOx passivation layer (≈4 nm) to improve surface smoothness and thermal stability. The resulting AlOx/ATO dielectric exhibits a high dielectric constant (κ ≈ 14) and a wide bandgap (Eg ≈ 4.7 eV). Exfoliated GaS FETs were fabricated on the AlOx/ATO dielectric with Ti/Au contact. Optical microscopy and AFM images confirm a smooth dielectric surface with an RMS roughness of ~0.6 nm, while the devices exhibit a low threshold voltage (Vth ≈ -0.05 V), high ON/OFF ratio (≈105), and photoresponsivity of R420 ≈ 3 × 102 AW-1, highlighting the potential of mist CVD-grown Al-Ti-O dielectric films.