Nitride-based 2DEG photodetectors with a large AC responsivity

Photocurrent characteristics of two-dimensional-electron-gas-based AlGaN/GaN metal-semiconductor-metal photodetectors

“…2. This 2DEG related peak was not observed with varying frequencies of light signals in the AlGaN/GaN photoconductive detector reported by Chang et al, 8 because photocurrent in photoconductive detector with a very high photoconductive gain is produced mainly in the entire AlGaN and GaN bulk regions and flows between two Ohmic contacts under uniform horizontally oriented electric field, and thus the thin 2DEG channel has very little contribution to the photocurrent response spectrum even at high frequencies. Moreover, photoresponse speed in the MSM structure is independent of the gap of interdigitated fingers due to the existence of the 2DEG channel, and hence the high-speed performance can be achieved without sacrificing the sensitivity in the 2DEG-based MSM photodetectors.…”

“…1-5 Among them, AlGaN/GaN photodetector has superiority over others in the development of highspeed optoelectronic integrated circuit because it can be easily integrated with matured AlGaN/GaN high electron mobility transistor ͑HEMT͒ devices in one epitaxial step. 6,7 Although several research groups [8][9][10] have contributed to the development of AlGaN/GaN photoconductive detector based on HEMT gate structure, this detector has very limited application due to its large dark current, poor UV/visible ratio and slow response time.…”

Suspended tungsten trioxide (WO3) gate AlGaN/GaN heterostructure deep ultraviolet detectors with integrated micro-heater

“…An AlGaN/GaN HEMT based UV detector with a maximum responsivity of ∼3000 A/W was first reported by Khan [13]. In recent years, responsivity values of ∼10 7 A/W under 365 nm illumination have been demonstrated [14,15]. It is found that the drain current and the 2DEG channel conductivity of AlGaN/GaN HEMTs increase under UV light illumination.…”

Structural and Electrical Characterization of Al[sub x]Ga[sub 1−x]N/GaN Interfaces for UV Photodetectors

“…The lower dark current in sample A is due to the use of a GaN capping layer that piezoelectrically enhanced the Schottky barrier height. 8 It has been reported that the dark current is lowered by a few orders of magnitude when a thin capping layer is used. However, the reduction in dark current in sample A is not very significant due to the presence of the high mobility channel at the interface.…”

“…With this vertical electric field, photogenerated electrons are compelled to move toward the Al x Ga 1−x N/GaN interface while photogenerated holes are repelled toward the substrate, which reduces the probability of recombination of the photogenerated carriers leading to an improved detector responsivity. 7,8 However, the polarization fields due to the high density of 2DEG at the interface also cause a high dark current when ohmic contacts are used as electrodes. 9 Thus, to reduce the dark current, Schottky contacts were used and it has been reported that the use of a GaN capping layer also helped in reducing the dark current.…”