Ultrasensitive and high-speed AlGaN/AlN solar-blind ultraviolet photodetector: a full-channel-self-depleted phototransistor by a virtual photogate

Abstract

High sensitivity, high solar rejection ratio, and fast response are essential characteristics for most practical applications of solar-blind ultraviolet (UV) detectors. These features, however, usually require a complex device structure, complicated process, and high operating voltage. Herein, a simply structured n-AlGaN/AlN phototransistor with a self-depleted full channel is reported. The self-depletion of the highly conductive n-AlGaN channel is achieved by exploiting the strong polarization-induced electric field therein to act as a virtual photogate. The resulting two-terminal detectors with interdigital Ohmic electrodes exhibit an ultrahigh gain of 1.3 × 10 5 , an ultrafast response speed with rise/decay times of 537.5 ps/3.1 μs, and an ultrahigh Johnson and shot noise (flicker noise) limited specific detectivity of 1.5 × 10 18 ( 4.7 × 10 16 ) Jones at 20-V bias. Also, a very low dark current of the order of ∼ pA and a photo-to-dark current ratio of above 10 8 are obtained, due to the complete depletion of the n - Al 0.5 Ga 0.5 N channel layer and the high optical gain. The proposed planar phototransistor combines fabrication simplicity and performance advantages, and thus is promising in a variety of UV detection applications.

Ultrahigh-Responsivity Ultraviolet Photodetectors Based on AlGaN/GaN Double-Channel High-Electron-Mobility Transistors

“…The specific detectivity (D*) is one of the most significant parameters and reveals the capability to detect weak optical signals from the noise. It can be calculated by the noise equivalent power (NEP): 34,35…”

“…The specific detectivity ( D * ) is one of the most significant parameters and reveals the capability to detect weak optical signals from the noise. It can be calculated by the noise equivalent power (NEP): , D * = A × B NEP , where A is the active area, B is the electrical bandwidth. Generally, the NEP of the device can be estimated according to the equation: ,,, NEP = 2 q I D R , where q is the electronic charge constant and I D is the dark current density, and then the specific detectivity D * was calculated to be 4.36 × 10 16 Jones at 2 V. However, this specific detectivity value was overestimated because it only considered the short noise, but the noise of PDs commonly includes shot noise, thermal noise, and flicker (1/ f ) noise. , In order to more precisely measure specific detectivity, it is crucial to take into account the contribution of flicker noise at low frequency.…”

“…It can be calculated by the noise equivalent power (NEP): , D * = A × B NEP , where A is the active area, B is the electrical bandwidth. Generally, the NEP of the device can be estimated according to the equation: ,,, NEP = 2 q I D R , where q is the electronic charge constant and I D is the dark current density, and then the specific detectivity D * was calculated to be 4.36 × 10 16 Jones at 2 V. However, this specific detectivity value was overestimated because it only considered the short noise, but the noise of PDs commonly includes shot noise, thermal noise, and flicker (1/ f ) noise. , In order to more precisely measure specific detectivity, it is crucial to take into account the contribution of flicker noise at low frequency. Figure a shows the noise power spectra of PD measured in the frequency range of 1 to 100 kHz at various drain voltages.…”

High-performance shortwave deep-UV response-enhanced photodetector based on nanoporous AlGaO/AlGaN with efficient light-harvesting

“…13 Profiting from the sophisticated material synthesis technology, the large bandgap modulation of the ternary materials above-mentioned is highly desired and is beginning to be explored to enhance the responsivity in the shortwave DUV band. 14,15 However, not only does the wider bandgap modulation largely introduce a great number of crystal defects that severely degrade the signal-to-noise ratio (SNR) of PDs, but also excessive bandgap results in an early cut-off in DUV detection. 16,17 More notably, light-harvesting capability is also crucial for highly sensitive DUV PDs, 18 but the performance of mainstream planar PDs based on bulk crystal and thin films is still restricted by the strong surface reflectivity.…”

Large‐Scale, Uniform‐Patterned CsCu2I3 Films for Flexible Solar‐Blind Photodetectors Array with Ultraweak Light Sensing

“…[3,4] The ultrawide-bandgap semiconductors, such as AlGaN and ZnMgO, have been extensively investigated in the deep UV PDs owing to their high absorption coefficients, [5,6] and high responsivity has been achieved in the corresponding phototransistors. [7][8][9] However, the alloying synthetic process of these materials is complex and expensive. High Al and Mg composition ratios in these AlGaN and ZnMgO alloys can reduce the crystal quality and lead to phase separation.…”