Transparent dual-band ultraviolet photodetector based on graphene/p-GaN/AlGaN heterojunction

Abstract

Versatile applications have driven a desire for dual-band detection that enables seeing objects in multiple wavebands through a single photodetector. In this paper, a concept of using graphene/p-GaN Schottky heterojunction on top of a regular AlGaN-based p-i-n mesa photodiode is reported for achieving solar-/visible-blind dual-band (275 nm and 365 nm) ultraviolet photodetector with high performance. The highly transparent graphene in the front side and the polished sapphire substrate at the back side allows both top illumination and back illumination for the dual band detection. A system limit dark current of 1×10−9 A/cm2 at a negative bias voltage up to -10 V has been achieved, while the maximum detectivity obtained from the detection wavebands of interests at 275 nm and 365 nm are ∼ 9.0 ×1012 cm·Hz1/2/W at -7.5 V and ∼8.0 × 1011 cm·Hz1/2/W at +10 V, respectively. Interestingly, this new type of photodetector is dual-functional, capable of working as either photodiode or photoconductor, when switched by simply adjusting the regimes of bias voltage applied on the devices. By selecting proper bias, the device operation mode would switch between a high-speed photodiode and a high-gain photoconductor. The device exhibits a minimum rise time of ∼210 µs when working as a photodiode and a maximum responsivity of 300 A/W at 6 μW/cm2 when working as a photoconductor. This dual band and multi-functional design would greatly extend the utility of detectors based on nitrides.

Unleashing the Power of Quantum Dots: Emerging Applications from Deep‐Ultraviolet Photodetectors for Brighter Futures

“…Although AlGaN has been widely used for DUV PDs based on their intrinsic bandgap tunability, most devices have focused on the 3D film type AlGaN. [26,[102][103][104] In 2021, Paramanik et al reported a DUV PD using an AlGaN/AlN QDs-in-wells structure, as illustrated in Figure 7g. [105] To selectively detect the DUV region, they constructed the MSM PDs which use horizontal carrier transport in AlGaN/AlN multiple quantum wells (MQW) (Figure 7h).…”

“…Although AlGaN has been widely used for DUV PDs based on their intrinsic bandgap tunability, most devices have focused on the 3D film type AlGaN. [ 26,102–104 ] In 2021, Paramanik et al. reported a DUV PD using an AlGaN/AlN QDs‐in‐wells structure, as illustrated in Figure 7g.…”

Polarization-doped n-p-i-p-n GaN-based parallel phototransistor with thick GaN absorption layer for achieving high responsivity

“…III-nitride semiconductor materials possess remarkable characteristics of wide energy bandgap, high thermal conductivity, large electron mobility, robust radiation resistance, and excellent chemical stability [1][2][3]. III-nitride-based ultraviolet (UV) photodetectors (PDs) have the potential for achieving high responsivity, fast response, and low dark current 5 Authors of equal contribution. * Authors to whom any correspondence should be addressed.…”

“…* Authors to whom any correspondence should be addressed. [4,5]. Moreover, the energy bandgap for (Al)GaN materials is adjustable that ranges from 3.4 eV to 6.2 eV covering 365 nm to 200 nm [6,7].…”

Highly Sensitive Ultraviolet Photodetector Based on an AlGaN/GaN HEMT with Graphene‐On‐p‐GaN Mesa Structure

“…[22,23] The addition of a p-GaN layer to the AlGaN/GaN changes the resulting p-GaN/AlGaN/GaN HEMT (enhancement-mode) from normally-on to normally-off through band bending and suppression of 2-DEG at zero-bias, which leads to low dark current. [31][32][33][34][35] In previously reported enhancementmode p-GaN/AlGaN/GaN photodetectors, the p-GaN acted as the gate by the means of photo induced carriers. However, there are only a very few studies on the utilization of p-GaN/ AlGaN/GaN structure, and most of them focused on phototransistor mode of operation, where the area of the p-GaN optical gate is limited by the transistor geometry.…”