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.

A fin field-effect transistor (FinFET) based on single β-Ga2O3 nanowire with a diameter of ∼60 nm transferred to Si substrate is demonstrated. The FinFET device shows good saturation performance within a drain-to-source voltage up to 5 V and exhibits a high on/off ratio of ∼4 × 108, a system-limit low leakage current (∼4 fA), and a relatively low subthreshold swing (∼110 mV). Simulation shows that the channel of the FinFET depletes much faster than that of the back-gate FET with negative gate bias, which is consistent with the measurement results. Moreover, trap-related 1/ f noise and 1/ f2 noise have been identified according to low frequency noise analysis, and a carrier number fluctuation is expected to be the dominant 1/ f noise mechanism in the β-Ga2O3 FinFET in this work.

Reduction in the size, weight, and power consumption of an infrared (IR) detection system (referred to as SWaP) is one of the critical challenges lying ahead for the development of nowadays IR detector technology, especially for Mid-/Long-wavelength IR wavebands, which calls for high operating temperature (HOT) IR photodetectors with good sensitivity that would ease the burden for the cooling systems. Emerging as strong competitors to HgCdTe detectors, antimonide (Sb)-based IR photodetectors and focal plane array (FPA) imagers have gradually stepped into real world applications after decades of development, thanks to their outstanding material properties, tunability of cut-off wavelengths, feasibility of device designs, and great potentials for mass production with low costs. Meanwhile, emerging demands of versatile applications seek for fast, compact and smart IR detection systems, in which integration of Sb-based IR photodetectors on the Si platform enables the direct information readout and processing with Si based microelectronics. This paper reviews recent progress in Sb-based HOT IR photodetectors and FPAs, which includes the fundamental material properties and device designs based on the bulk InAsSb, InAs/GaSb and InAs/InAsSb type-II superlattices, together with the cutting-edge performance achieved. This work also covers the new trends of development in the Sb-based IR photodetectors like optical engineering for signal harvesting, photonic integration techniques, as well as MOCVD growth of antimonides. Finally, challenges and possible solutions for future works are provided from the perspectives of material growth, device design and imaging system. These new advances may cast light on designs and strategies for achieving HOT devices at thermoelectric cooling temperatures (yet with lower costs) by identifying existing challenges, and find more extensive emerging applications.

In this work, low frequency noise in β-Ga2O3 nanowire-based (NW) electronic devices is analyzed, which exhibits different behaviors as the device size scales down. The noise spectrum for the narrower NW (∼80 nm) is closer to 1/f characteristics, whereas it starts to show evident 1/f2 components as the NW size gets thicker (∼200 nm), giving clear signs of distinctive features for the bunch of traps at the NW interface or in the bulk. Our results show that 1/f noise in these NW electronic devices seems predominantly originated from an aggregated effect of the intricate trap states close to the β-Ga2O3 NW surface or interface with a wide range distribution, while finite groups of active deep traps play a critical role in contributing 1/f2components via generation-recombination or random telegraph signal processes. Notably, as the bias voltage increases, the 1/f2 components in the noise spectra get more overwhelming and would shift toward lower frequencies, suggesting that electric ionization effects would screen the shallow traps close to the surface or interface based on the Poole–Frenkel model. The Hooge's constants extracted from the 1/f noise component for these β-Ga2O3 NW-based devices fall in the range of 0.008–0.019, which are comparable to those of the best reported devices based on other wide bandgap semiconductor with nanoscale structures, including GaN, ZnO, and SnO2. This work may give hints of revealing the sophisticated dynamic behaviors of traps in the surface/volume β-Ga2O3 materials and electronic devices in the nanoscale by low frequency noises.