A voltage-controlled tunable two-color infrared photodetector using GaAs/AlAs/GaAlAs and GaAs/GaAlAs stacked multiquantum wells

A voltage-controlled tunable two-color infrared detector with photovoltaic (PV) and photoconductive (PC) dual-mode operation at 3-5 mu m and 8-14 mu m using GaAs/AlAs/AlGaAs double barrier quantum wells (DBQWs) and bound-to-continuum GaAs/AlGaAs quantum wells is demonstrated. The photoresponse peak of the photovoltaic GaAs/AlAs/GaAlAs DBQWs is at 5.3 mu m, and that of the photoconductive GaAs/GaAlAs quantum wells is at 9.0 mu m. When the two-color detector is under a zero bias, the spectral response at 5.3 mu m is close to saturate and the peak detectivity at 80 K can reach 1.0X10(11) cmHz(1/2)/W, while the spectral photoresponsivity at 9.0 mu m is absolutely zero completely. When the external voltage of the two-color detector is changed to 2.0 V, the spectral photoresponsivity at 5.3 mu m becomes zero while the spectral photoresponsivity at 9.0 mu m increases comparable to that at 5.3 mu m under zero bias, and the peak detectivity (9.0 mu m) at 80 K can reach 1.5X10(10) cmHz(1/2)/W. Strictly speaking, this is a real bias-controlled tunable two-color infrared photodetector. We have proposed a model based on the PV and PC dual-mode operation of stacked two-color QWIPs and the effects of tunneling resonance with narrow energy width of photoexcited electrons in DBQWs, which can explain qualitatively the voltage-controlled tunable behavior of the photoresponse of the two-color infrared photodetector. (C) 1996 American Institute of Physics.

A voltage-controlled ring oscillator using InP full enhancement-mode HEMT logic

A voltage-controlled ring oscillator (VCO) based on a full enhancement-mode InAIAs/InGaAs/InP high electron mobility transistor (HEMT) logic is proposed. An enhancement-mode HEMT (E-HEMT) is fabricated, whose threshold is demonstrated to be 10 mV. The model of the E-HEMT is established and used in the SPICE simulation of the VCO. The result proves that the full E-HEMT logic technology can be applied to the VCO. And compared with the HEMT DCFL technology, the complexity of our fabrication process is reduced and the reliability is improved.

Annealing ambient controlled deep defect formation in InP

Deep defects in annealed InP have been investigated by deep level transient capacitance spectroscopy (DLTS), photo induced current transient spectroscopy (PICTS) and thermally stimulated current spectroscopy (TSC). Both DLTS results of annealed semiconducting InP and PICTS and TSC results of annealed semi-insulating InP indicate that InP annealed in phosphorus ambient has five defects, while lid? annealed in iron phospbide ambient has two defects. Such a defect formation phenomenon is explained in terms of defect suppression by the iron atom diffusion process. The correlation of the defects and the nature of the defects in annealed InP are discussed based on the results.

The role of zinc dopant and the temperature effect on the controlled growth of InNnanorods in metal-organic chemical vapor deposition system

This work was supported by the National Science Foundation of China (60976008 and 60776015), the Special Funds for Major State Basic Research Project (973 program) of China (2006CB604907), and the 863 High Technology R&D Program of China (2007AA03Z402 and 2007AA03Z451). The authors express their appreciations to Prof. Yongliang Li (Analytical and Testing Center, Beijing Normal University) for FE-SEM measurements, to DrTieying Yang and Prof. Huanhua Wang (Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences) for XRD measurements and helpful discussions.

Fracture of colloidal single-crystal films fabricated by controlled vertical drying deposition

Controlled vertical drying deposition method was used to make high-quality single crystal close-packed colloidal films formed of different radii polystyrene latex spheres on glass substrates coming from a low concentration water suspension (0.1% volume fraction). Regardless of the spheres radii the film thickness was about 6.3 microns. However, cracks destroyed the crystalline film structure during the colloidal film growth. The effect of particle radius (85-215 nm range) on film cracking was systematically studied using in situ optical fracture monitoring. Primary parallel cracks run along the vertical growth direction, later followed by secondary branched cracks in-between the primary cracks due to residual water evaporation. Quantitative theoretical relationship between the cracks spacing and particles radius was derived and shows good agreement with experimental observations. Normalized cracks spacing is related to a reciprocal ratio of the dimensionless particle radius.

Controlled synthesis and diameter-dependent optical properties of Cu nanowire arrays

Using electrochemical deposition, Cu nanowire arrays have been successfully fabricated by home-made polycarbonate ion-track templates. The diameters were well controlled by etching time of templates. The minimum diameter is 15 nm. The morphologies and structures were analyzed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The wires prefer [1 1 0] growth direction due to H ions absorption. The optical properties of Cu nanowire arrays are studied by an ultraviolet/visible/near-infrared spectrophotometer. Two extinction peaks were observed in spectra. The optical mechanism is discussed based on surface plasmon resonance