AlGaN/GaN HEMT-Based MHM Ultraviolet Phototransistor With Bent-Gate Structure

Abstract

We have designed an AlGaN/GaN-based metal-heterostructure-metal (MHM) ultraviolet (UV) phototransistor (PT) with bent-Gate Structure. After partial etching of the AlGaN/GaN layer, an interdigital Ti/Al/Ni/Au metal stack was deposited on the GaN absorber layer to form an ohmic contact, which is in lateral contact with the AlGaN/GaN heterojunction to form a MHM structure. A bent gate was embedded between the interdigital ohmic electrodes to control the switching state of the two-dimensional electron gas (2DEG) channel. More importantly, benefiting from the strong polarization electric field in the lengthwise direction and the 2DEG high mobility channel in the lateral direction at the AlGaN/GaN heterojunction interface of the device, the device shows excellent photodetection performance: a peak responsivity (R) of $6 \times 10^{{4}}$ A/W can be obtained under 265 nm UV irradiation, with a corresponding detectivity (D $^{\ast }$ ) of $8.28 \times 10^{{16}}~\text {cm}\cdot \text {W}^{-{1}}\cdot \text {Hz}^{\text {1/2}}$ ; and a responsivity of $1.8 \times 10^{{4}}$ A/W can be obtained under 360 nm UV irradiation, with a corresponding D $^{\ast }$ of $2.48 \times 10^{{16}}~\text {cm}\cdot \text {W}^{-{1}} \cdot \text {Hz}^{\text {1/2}}$ . In addition, we have analyzed and investigated the operating principle of the designed device and the control mechanism of the bent gate using the theoretically simulated results of the device.