Ultrahigh detectivity, high-speed and low-dark current AlGaN solar-blind heterojunction field-effect phototransistors realized using dual-float-photogating effect

Abstract

High detectivity is essential for solar-blind deep-ultraviolet (DUV) light detection because the DUV signal is extremely weak in most applications. In this work, we report ultrahigh-detectivity AlGaN-based solar-blind heterojunction-field-effect phototransistors fabricated utilizing dual-float-photogating effect. The p + - Al 0.4 GaN layer and Al 0.4 GaN absorber layer deposited on the Al 0.6 GaN barrier serve as top pin-junction photogate, while the thin Al 0.4 GaN channel layer with a strong polarization field inside acts as virtual back photogate. Due to the effective depletion of the two-dimensional electron gas at the Al 0.6 Ga 0.4 N / Al 0.4 Ga 0.6 N heterointerface by the top photogate, the dark current was suppressed below 2 pA in the bias range of 0 to 10 V. A high photo-to-dark current ratio over 10 8 and an optical gain of 7.5 × 10 4 were demonstrated at a bias of 5 V. Theoretical analysis indicates that the optical gain can be attributed to the joint action of the floating top and back photogates on the channel current. As a result, a record high flicker noise (Johnson and shot noise) limited specific detectivity of 2.84 × 10 15 ( 2.91 × 10 17 ) cm Hz 0.5 W − 1 was obtained. Furthermore, high response speed at the microsecond level was also shown in the devices. This work provides a promising and feasible approach for high-sensitivity DUV detection.

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): , 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.…”

Application of Perovskite as Solution‐Processed Solid Electrolyte in Polymer Electrochemical Transistor

“…This may be related to the floating gate effect introduced by the PEO layer, which changes the electric field and thus affects the doping process. [ 37 ]…”

“…This may be related to the floating gate effect introduced by the PEO layer, which changes the electric field and thus affects the doping process. [37] To investigate the effect of UV illumination on the polymer electrochemical transistors, an electrochemical cell was fabricated and tested as shown in Figure 4e. The results of cyclic voltammetry show that the oxidation potential of MEH-PPV decreased from 0.404 to 0.366 V under UV illumination (Figure 4f).…”

Demonstration of Spectral Selectivity of Efficient and Ultrafast GaN/AlGaN-Based Metal–Semiconductor–Metal Ultraviolet Photodiodes

“…where D * is spectral detectivity in Jones, A is active area of the device, and BW = 12.5 GHz is the measurement bandwidth as specified in [24] and [25] determined from Fig. From Table 1 we can see that the Pt intrinsic Al0.1Ga0.9N device exhibited better spectral responsivity than the Au intrinsic Al0.1Ga0.9N device.…”