2018年1月31日星期三

Infrared imaging technique operates at high temperatures


From aerial surveillance to cancer detection, mid-wavelength infrared (MWIR) radiation has a wide range of applications. And as the uses for high-sensitivity, high-resolution imaging continue to expand, MWIR sources are becoming more attractive.

Currently, commercial technologies for MWIR detection, such as indium antimonide (InSb) and mercury-cadmium-telluride (MCT), can only operate at cryogenic temperatures in order to reduce thermal and electrical noise. In a search for alternatives, a team of researchers at Northwestern University's Center for Quantum Devices (CQD) has incorporated new materials to develop detectors that can work at room temperature.

"A higher operating temperature eliminates the need for liquid nitrogen," said Manijeh Razeghi, Walter P. Murphy Professor of Electrical Engineering and Computer Science and director of the CQD at Northwestern's McCormick School of Engineering and Applied Science. "That makes detectors more compact, less expensive, and more portable."
Depending on its use, infrared radiation is divided into several wavelength segments. MWIR have a radiation range between 3-5 microns; cameras able to see in this wavelength are capable of passive infrared imaging.
Razeghi and her group developed an indium arsenide/gallium antimonide (InAs/GaSb) type II superlattice that demonstrated high-resolution MWIR images while operating at high temperatures. The new technique was particularly successful at obtaining infrared images of the human body, which has potential for vascular imaging and disease detection.
Supported by DARPA, the Army Research Laboratory, Air Force Research Laboratory, and NASA, the team's findings were reported in paper in the January 1 issue of Optics Letters, the journal of the Optical Society of America.
Source:PHYS
For more information about GaSb, please visit our website:www.powerwaywafer.com,send us email at: angel.ye@powerwaywafer.com or  or powerwaymaterial@gmail.com.


2018年1月24日星期三

Semiconductor band gap localization via Gaussian function

To determine the band gap of bulk semiconductors with transmission spectroscopy alone is considered as an extremely difficult task because in the higher energy range, approaching and exceeding the band gap energy, the material is opaque yielding no useful data to be recorded. In this paper, by investigating the transmission of industrial GaSb wafers with a thickness of 500 µm, we demonstrate how these obstacles of transmission spectroscopy can be overcome. The key is the transmission spectrums' derivative, which coincides with the Gaussian function. This understanding can be used to transfer Beers' law in an integral form opening the pathway of band gap determinations based on mathematical parameters only. The work also emphasizes the correlation between the thermal band gap variation and Debye temperature.


soource:Iopscience




Electrical and optical performances with extracted minority carrier lifetimes of InAs/GaSb SL photodetector operating in the mid wavelength infrared range

Highlights

Optical and electrical performance of InAs/GaSb based T2SL detector are analysed.
The T2SL structure is designed to operate with high quantum efficiency in the MWIR.
Band structure of T2SL are analysed by SEPM calculations.
Minority carrier lifetimes are highly important for understanding of carrier transport and improving the device performance.
Shockley Model is used to extract the minority carrier lifetimes from temperature dependence of J-V measurements.

Abstract

We report a study on the temperature dependence of electrical and optical performance of InAs/GaSb based type-II superlattice (T2SL) pin photodetectors in the mid wavelength infrared range (MWIR). The SL structure exhibits an optical response of 50% cut-off wavelength at 4.9 μm at 79 K. Deduced from current density–voltage (J–V) measurements, dark current density under 0.1 V reverse bias is measured as 7.6 × 10−6 A/cm2 with a corresponding differential–resistance–area product (R0A) of 3.3 × 104 Ωcm2 at 100 K. Minority carrier lifetimes of the T2SL detectors are analysed by Shockley's Model where experimental data for dark current densities are fitted by diffusion and generation-recombination (GR) components at different temperatures.

source:ScienceDirect
For more information about GaSb, please visit our website:www.powerwaywafer.com,send us email at: angel.ye@powerwaywafer.com or  or powerwaymaterial@gmail.com.

2018年1月17日星期三

Mid-IR GaSb-based monolithic vertical-cavity surface-emitting lasers

We present a detailed study of GaSb-based monolithic vertical-cavity surface-emitting lasers (VCSELs) targeting an emission near 2.3 µm. These VCSELs rely on two n-type epitaxial semiconductor Bragg-mirrors and on a tunnel-junction for electron-hole conversion. Bragg mirror and active region designs, epitaxial material properties, device modelling, fabrication and performances are all addressed in order to fully assess the potential of this technology. Monolithic aperture-VCSELs, where carrier confinement is ensured by selective under-etching of the tunnel junction, have been fabricated in both bipolar-cascade VCSEL as well as single-stage VCSEL configurations. All devices have been thoroughly characterized and experimental data have been analysed in light of modelling trends. Our results give new insights into the physics of GaSb monolithic VCSELs and provide keys to their successful design. Further, they show that this technology is a viable option for tunable mid-infrared sources.

soource:iopscience