MoS₂–InGaZnO Heterojunction Phototransistors with Broad\nSpectral Responsivity

Abstract

We\nintroduce an amorphous indium–gallium–zinc-oxide\n(<i>a</i>-IGZO) heterostructure phototransistor consisting\nof solution-based synthetic molybdenum disulfide (few-layered MoS₂, with a band gap of ∼1.7 eV) and sputter-deposited <i>a</i>-IGZO (with a band gap of ∼3.0 eV) films as a novel\nsensing element with a broad spectral responsivity. The MoS₂ and <i>a</i>-IGZO films serve as a visible light-absorbing\nlayer and a high mobility channel layer, respectively. Spectroscopic\nmeasurements reveal that appropriate band alignment at the heterojunction\nprovides effective transfer of the visible light-induced electrons\ngenerated in the few-layered MoS₂ film to the underlying <i>a</i>-IGZO channel layer with a high carrier mobility. The photoresponse\ncharacteristics of the <i>a</i>-IGZO transistor are extended\nto cover most of the visible range by forming a heterojunction phototransistor\nthat harnesses a visible light responding MoS₂ film with\na small band gap prepared through a large-area synthetic route. The\nMoS₂–IGZO heterojunction phototransistors exhibit\na photoresponsivity of approximately 1.7 A/W at a wavelength of 520\nnm (an optical power of 1 μW) with excellent time-dependent\nphotoresponse dynamics.