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Articles you may be interested inHigh operating temperature interband cascade midwave infrared detector based on type-II InAs/GaSb strained layer superlattice Appl. Phys. Lett. 101, 021106 (2012); 10.1063/1.4733660Interband cascade infrared photodetectors with enhanced electron barriers and p-type superlattice absorbers Assessment of quantum dot infrared photodetectors for high temperature operation J. Appl. Phys.Device simulation for Ga As ∕ Al Ga As superlattice infrared photodetector with a single current blocking layer Interband-cascade infrared photodetectors ͑ICIPs͒, composed of discrete superlattice absorbers, are demonstrated at temperatures up to 350 K with a cutoff wavelength near 5 m at 80 K to beyond 7 m above room temperature. The peak responsivity exceeds 200 mA/W, higher than the values reported from early interband cascade laser structures, suggesting a significantly enhanced quantum efficiency of the superlattice absorbers. A theoretical model, originally developed for quantum well infrared photodetectors ͑QWIPs͒, is applied to ICIPs to analyze their device performance. The Johnson-limited and background-limited detectivities are extracted and indicate that background-limited performance temperatures for two ICIP structures are 126 and 105 K at 5 m. It is expected that optimized ICIPs will provide improved performance by combining the advantages of conventional photodiodes and the discrete nature of QWIPs and IC lasers.

A theoretical framework for studying signal and noise in multiple-stage interband infrared photovoltaic devices is presented. The theory flows from a general picture of electrons transitioning between thermalized reservoirs. Making the assumption of bulk-like absorbers, we show how the standard semiconductor transport and recombination equations can be extended to the case of multiple-stage devices. The electronic noise arising from thermal fluctuations in the transition rates between reservoirs is derived using the Shockley-Ramo and Wiener-Khinchin theorems. This provides a unified noise treatment accounting for both the Johnson and shot noise. Using a Green's function formalism, we derive consistent analytic expressions for the quantum efficiency and thermal noise in terms of the design parameters and macroscopic material properties of the absorber. The theory is then used to quantify the potential performance improvement from the use of multiple stages. We show that multiple-stage detectors can achieve higher sensitivities for applications requiring a fast temporal response. This is shown by deriving an expression for the optimal number of stages in terms of the absorption coefficient and absorber thicknesses for a multiple-stage detector with short absorbers. The multiple-stage architecture may also be useful for improving the sensitivity of high operating temperature detectors in situations where the quantum efficiency is limited by a short diffusion length. The potential sensitivity improvement offered by a multiple-stage architecture can be judged from the product of the absorption coefficient, α, and diffusion length, Ln, of the absorber material. For detector designs where the absorber lengths in each of the stages are equal, the multiple-stage architecture offers the potential for significant detectivity improvement when αLn ≤ 0.2. We also explore the potential of multiple-stage detectors with photocurrent-matched absorbers. In this architecture, the absorbers are designed to absorb and collect an equal number of carriers in each stage. It is shown that for zero-bias operation, this design has a higher ultimate detectivity than a single-absorber device. Such improvements in detectivity are significant for material with αLn ≤ 0.5. Using the results derived for general values of αLn, we offer an outlook for multiple-stage detectors that utilize InAs/GaSb superlattice absorbers.

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We present results on the optical and electrical performance of mid-infrared detectors based on interband-cascade structures. These devices include enhanced electron barriers, designed to suppress intraband-tunneling current between stages, and p-doped type-II InAs/GaSb superlattice absorbers. Within the sample set, we examined devices with different absorber thicknesses and doping levels. Carriers are extracted less efficiently in devices with longer absorbers, which is attributed to more band bending within the absorber due to electric charge accumulation. Also, devices with lower-doped (1 × 1017 cm−3) absorbers are found to have better optical and electrical performances than those with higher levels of doping (3 × 1017 cm−3). The overall performance of these devices was superior to previously reported results, with Johnson-noise limited detectivities, at 4.0 μm, as high as 6.0 × 1012 and 2.5 × 1011 Jones at 80 and 150 K, respectively.

Hepatocellular carcinoma (HCC) is an immunotherapy-resistant malignancy characterized by high cellular heterogeneity. The diversity of cell types and the interplay between tumor and non-tumor cells remain to be clarified. Single cell RNA sequencing of human and mouse HCC tumors revealed heterogeneity of cancer-associated fibroblast (CAF). Cross-species analysis determined the prominent CD36+ CAFs exhibited high-level lipid metabolism and expression of macrophage migration inhibitory factor (MIF). Lineage-tracing assays showed CD36+CAFs were derived from hepatic stellate cells. Furthermore, CD36 mediated oxidized LDL uptake-dependent MIF expression via lipid peroxidation/p38/CEBPs axis in CD36+ CAFs, which recruited CD33+myeloid-derived suppressor cells (MDSCs) in MIF- and CD74-dependent manner. Co-implantation of CD36+ CAFs with HCC cells promotes HCC progression in vivo. Finally, CD36 inhibitor synergizes with anti-PD-1 immunotherapy by restoring antitumor T-cell responses in HCC. Our work underscores the importance of elucidating the function of specific CAF subset in understanding the interplay between the tumor microenvironment and immune system.

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