Comprehensive analysis of optoelectronic performance of ultraviolet phototransistors based on AlGaN/GaN heterostructure

Abstract

Optoelectronic performance of ultraviolet phototransistors (UVPTs) based on AlGaN/GaN high-electron-mobility transistor (HEMT) configuration is comprehensively studied under different illumination wavelengths, light power densities, gate biases, and drain voltages. A special photoresponse mechanism combining photovoltaic effect and photoconductive effect is proposed to explain the variation of detection performance with the optical and electrical conditions. By comparing the photoreponse characteristics under typical illumination wavelengths of 310 nm and 360 nm, the optoelectronic properties of the HEMT-based UVPTs are deeply revealed and summarized. This work can provide suggestions and guidelines for designing of AlGaN/GaN-based UVPTs in III-V integrated photonic systems.

100 mV Ultra-Low Bias AlGaN/GaN Photodetector Based on Fin-Shaped Capacitor Configuration for Future Integrated Optoelectronics

“…Apart from PDCR and responsivity, specific detectivity D* is also calculated to quantitively assess the sensitivity performance of the photodetector. Assuming that the total noise is primarily caused by the shot noise from the dark current, and the measurements of the photocurrents and dark current were done under the same filtering condition, D* can be determined by 41,42 * = i k j j j j j y { z z z z z D R A qI 2 dark 0.5 (4) where A denotes the photodetector active area. Using the peak responsivity at 1 × 10 −3 mW/cm 2 , detectivities of this device at different bias voltages are calculated and plotted in Figure 3e.…”

“…Substantial effort has been directed into the development of ultraviolet (UV) photodetectors on epitaxy heterojunctionsaluminum gallium nitride/gallium nitride (AlGaN/GaN) platforms in the past three decades. − As representatives of wide band gap semiconductors, AlGaN and GaN feature intrinsic visible-blind optoelectronic characteristics, as well as properties like high physical and chemical stability, high radiation and high temperature tolerance, etc. , Compared with pure GaN or AlGaN, the heterojunction AlGaN/GaN further acquires high electron concentration and high electron mobility due to the existence of two-dimensional electron gas (2DEG) at the heterointerface. − Therefore, unprecedentedly good performances such as ultra-high photo-to-dark current ratio (PDCR), high gain, and high responsivity have been embodied by AlGaN/GaN-based phototransistors and detectors . For example, the p-GaN/AlGaN/GaN phototransistor proposed by Wang et al exhibits a high PDCR of 1.4 × 10 11 and a great UV/visible rejection ratio of 4.8 × 10 7 .…”

“…However, these superior performances depend primarily on the bias voltage applied to these devices. The typical working bias of these AlGaN/GaN-based UV phototransistors and detectors is in a range from 5 to 15 V. ,− For some designs of phototransistors (except the floating p-GaN gated structures), ,, additional gate bias around 5 V is also required. ,,, Hypothetically, if these devices were to be biased below 500 mV, up to 60–99% performance degradation would manifest in their applications.…”

“…7−9 Therefore, unprecedentedly good performances such as ultra-high photo-to-dark current ratio (PDCR), high gain, and high responsivity have been embodied by AlGaN/GaN-based phototransistors and detectors. 4 For example, the p-GaN/AlGaN/GaN phototransistor proposed by Wang et al 10 exhibits a high PDCR of 1.4 × 10 11 and a great UV/visible rejection ratio of 4.8 × 10 7 . Zhang et al 11 demonstrated a Ni/Au-gated AlGaN/GaN phototransis-tor with an extremely high responsivity of 3.6 × 10 7 A/W toward 265 nm UV.…”

Demonstration of p-GaN/AlGaN/GaN-based ultraviolet phototransistors with sub-saturated transfer characteristics

“…Among them, GaNbased high-electron-mobility transistors (HEMTs) have received more attention for high-efficiency UV PDs [4][5][6]. Thanks to the high-density two-dimensional electron gas (2DEG) in the interface of AlGaN/GaN heterostructure, an ultrahigh photoresponsivity and ultrafast photoresponse can be observed in the HEMT-based UV PDs [7][8][9]. In addition, the transistor operation provides the HEMT-based UV PDs 1 Dingbo Chen and Penghao Zhang contribute equally to this paper.…”