Enhanced LWIR response of InP/InAsP quantum discs-in-nanowire array photodetectors by photogating and ultra-thin ITO contacts.

Here we report on an experimental and theoretical investigation of the long-wavelength infrared (LWIR) photoresponse of photodetectors based on arrays of three million InP nanowires with axially embedded InAsP quantum discs. An ultra-thin top indium tin oxide contact combined with a novel photogating mechanism facilitates an improved LWIR normal incidence sensitivity in contrast to traditional planar quantum well photodetectors. The electronic structure of the quantum discs, including strain and defect-induced photogating effects, and optical transition matrix elements were calculated by an 8-bandk·psimulation along with solving drift-diffusion equations to unravel the physics behind the generation of narrow linewidth intersubband signals observed from the quantum discs.

The Effect of Self-Care Nurturance Using the Theory of Modeling and Role-Modeling on Self-Efficacy in Stroke Patients: A Randomized Controlled Trial.

The disability after a stroke results in reduced self-care capacity and lower levels of self-efficacy in survivors. Exploiting a holistic self-care plan to strengthen internal resources in clients can be thus deemed as an effective solution. This study aimed to determine the effect of self-care nurturance using the Theory of Modeling/Role-Modeling (TMRM) on self-efficacy in stroke clients. A randomized controlled trial was conducted at Qaem Hospital, Mashhad, Iran, in 2020. For this purpose, 70 clients were randomly assigned to 2 groups. Then, the experimental group received self-care nurturance based on the TMRM, all through 4 to 6 individual sessions of 30 to 45 minutes in the hospital, and subsequently 2 sessions of telephone counseling up to 8 weeks after the discharge. With reference to patient evaluation in terms of self-care resources, knowledge, and actions, the researcher also tried to strengthen such factors based on the individual needs of each client. The control group received routine care. The data were collected through completing a demographic/disease information form at the onset and the Stroke Self-Efficacy Questionnaire (SSEQ) before the intervention, 4 and 8 weeks after it. The results revealed that the self-efficacy mean scores of the experimental group, in the course of 3 measurement stages, had significantly improved, compared with that in the control group (P = .018). It was concluded that applying the TMRM could strengthen internal and external resources and self-care knowledge in stroke patients, develop their self-care actions, and improve their levels of self-efficacy.

Monolithic InSb nanostructure photodetectors on Si using rapid melt growth.

Monolithic integration of InSb on Si could be a key enabler for future electronic and optoelectronic applications. In this work, we report the fabrication of InSb metal-semiconductor-metal photodetectors directly on Si using a CMOS-compatible process known as rapid melt growth. Fourier transform spectroscopy demonstrates a spectrally resolved photocurrent peak from a single crystalline InSb nanostructure with dimensions of 500 nm × 1.1 µm × 120 nm. Time-dependent optical characterization of a device under 1550 nm illumination indicated a stable photoresponse with responsivity of 0.50 A W-1 at 16 nW illumination, with a time constant in the range of milliseconds. Electron backscatter diffraction spectroscopy revealed that the single crystalline InSb nanostructures contain occasional twin defects and crystal lattice twist around the growth axis, in addition to residual strain, possibly causing the observation of a low-energy tail in the detector response extending the photosensitivity out to 10 µm wavelengths (0.12 eV) at 77 K.

Gain and bandwidth of InP nanowire array photodetectors with embedded photogated InAsP quantum discs.

Here we report on the experimental results and advanced self-consistent real device simulations revealing a fundamental insight into the non-linear optical response of n+-i-n+ InP nanowire array photoconductors to selective 980 nm excitation of 20 axially embedded InAsP quantum discs in each nanowire. The optical characteristics are interpreted in terms of a photogating mechanism that results from an electrostatic feedback from trapped charge on the electronic band structure of the nanowires, similar to the gate action in a field-effect transistor. From detailed analyses of the complex charge carrier dynamics in dark and under illumination was concluded that electrons are trapped in two acceptor states, located at 140 and 190 meV below the conduction band edge, at the interface between the nanowires and a radial insulating SiOx cap layer. The non-linear optical response was investigated at length by photocurrent measurements recorded over a wide power range. From these measurements were extracted responsivities of 250 A W-1 (gain 320)@20 nW and 0.20 A W-1 (gain 0.2)@20 mW with a detector bias of 3.5 V, in excellent agreement with the proposed two-trap model. Finally, a small signal optical AC analysis was made both experimentally and theoretically to investigate the influence of the interface traps on the detector bandwidth. While the traps limit the cut-off frequency to around 10 kHz, the maximum operating frequency of the detectors stretches into the MHz region.