High-performance broadband infrared (IR)/terahertz (THz) detection is crucial in many optoelectronic applications. However, the spectral response range of semiconductor-based photodetectors is limited by the bandgaps. This paper proposes a ratchet structure based on the GaAs/Al _x Ga _{1− x} As heterojunction, where the quasi-stationary hot hole distribution and intravalence band absorption from light or heavy hole states to the split-off band overcome the bandgap limit, ensuring an ultrabroadband photoresponse from near-IR to THz region (4 to 300 THz). The peak responsivity of the proposed structure can reach 7.3 A/W, which is five orders of magnitude higher than that of the existing broadband photon-type detector. Because of the ratchet effect, the proposed photodetector has a bias-tunable photoresponse characteristic and can operate in the photovoltaic mode with a broad photocurrent spectrum (18 to 300 THz). This work not only demonstrates a broadband photon-type THz/IR photodetector but also provides a method to study the light-responsive ratchet.

An ultra-broadband upconversion device is demonstrated by direct tandem integration of a p-type GaAs/Al_xGa_1-xAs ratchet photodetector (RP) with a GaAs double heterojunction light emitting diode (DH-LED) using the molecular beam epitaxy. An ultra-broadband photoresponse from the terahertz (THz) to near-infrared (NIR) region (4–200 THz) was realized, which covered a much wider frequency range compared with existing upconversion devices. Broadband IR/THz radiation from a 1000 K blackbody was upconverted into NIR light that could be detected via a commercial Si-based device. The normal incidence absorption of the RP simplified the structure of the RP-LED device and made it more compact than the intersubband transition-based upconverters. In addition to upconversion, the proposed upconverter was investigated as a photovoltaic detector in the infrared region (detection range from 18 to 150 THz) based on the ratchet effect without an applied bias voltage.

Transistor reliability characterization studies are reported for a state of the art 22nm 3-D tri-gate HK/MG SoC technology with logic and HV I/O transistor architecture. TDDB, BTI and HCI degradation modes for logic and I/O transistors are studied and excellent reliability is demonstrated. In order to simultaneously integrate logic and HV 3-D tri-gate transistors with robust reliability, the importance of process optimization is emphasized.

Multi-color terahertz (THz) detector has attracted much attention in various applications because of the ability to obtain more comprehensive information simultaneously. THz quantum well photodetectors (QWPs) have great advantages in realizing multi-color detection because of high speed, sensitivity, and mature technology. In this work, QWPs based on antenna coupled microcavity (AM-QWP) and etched antenna coupled microcavity (EAM-QWP) structures are proposed to realize multi-color THz detection. Thanks to the combination of the microcavity resonance and surface plasmon polariton mode, AM-QWP achieves a coupling efficiency of one order of magnitude higher than that of the conventional 45° edge facet coupler (45°-QWP) in multiple bands. The EAM-QWP only retains the active region where the effective photocurrent is generated so that the coupling light is highly localized in a small area, improving the optical coupling efficiency by two orders higher compared with 45°-QWP. It is theoretically estimated that the responsivity of AM-QWP and EAM-QWP at the temperature of 4 K is 9.6–24.0 A/W and 78.4–196.0 A/W while their noise equivalent power (NEP) is 5.4 × 10⁻⁴–1.1 × 10⁻³ pW/Hz^1/2 and 1.7 × 10⁻⁵–3.5 × 10⁻⁵ pW/Hz^1/2, and the specific detectivity is 4.4 × 10¹²–8.9 × 10¹² and 6.9 × 10¹³–1.4 × 10¹⁴ cm Hz^1/2/W, respectively. This work provides a guideline for the experimental realization of high-performance multi-color THz QWPs.

High-performance infrared thermal imaging devices are widely used in military, biomedical and other fields. Upconversion pixel-less imaging is promising for infrared imaging. In this paper, we propose a hybrid metasurface to achieve high upconversion efficiency of the integrated quantum well infrared photodetector and light-emitting diodes (QWIP-LED). Systematical investigations on the performance of the QWIP-LED, including optical coupling efficiency, light extraction efficiency, and upconversion efficiency, have been carried out via theoretical simulation. We also present the integration time for different devices with different optical coupling structures. Numerical results show that 45° edge-coupled QWIP-LED is not suitable for imaging applications for the low upconversion efficiency. Traditional grating-coupled QWIP-LED can be optimized for real-time thermal imaging. The hybrid-metasurface-based QWIP-LED can achieve a high frame rate above 300 Hz due to the enhanced upconversion efficiency. This work gives a precise description of QWIP-LED performance with different device structures and opens the way for large format upconversion pixel-less imaging.