J. L. Schmit

Bio: J. L. Schmit is an academic researcher. The author has contributed to research in topics: Band gap. The author has an hindex of 1, co-authored 1 publications receiving 565 citations.

Energy gap versus alloy composition and temperature in Hg1−xCdxTe

Abstract: We have used the data from 22 different studies to derive a new empirical expression for the energy band gap (Eg) of Hg1−xCdxTe: Eg =−0.302+1.93x+5.35(10−4)T(1−2x) −0.810x2+0.832x3. This expression is valid over the full composition range and for temperatures from 4.2 to 300 K. The standard error of estimate is 0.013 eV, which is at least 15% better than that of previously reported expressions.

HgCdTe infrared detector material: history, status and outlook

Abstract: This article reviews the history, the present status and possible future developments of HgCdTe ternary alloy for infrared (IR) detector applications. HgCdTe IR detectors have been intensively developed since the first synthesis of this material in 1958. This article summarizes the fundamental properties of this versatile narrow gap semiconductor, and relates the material properties to its successful applications as an IR photoconductive and photovoltaic detector material. An emphasis is put on key developments in the crystal growth and their influence on device evolution. Competitive technologies to HgCdTe ternary alloy are also presented. Recent advances of backside illuminated HgCdTe heterojunction photodiodes have enabled a third generation of multispectral instruments for remote sensing applications and have led to the practicality of multiband IR focal plane array technology. Finally, evaluation of HgCdTe for room temperature long wavelength IR applications is presented. (Some figures in this article are in colour only in the electronic version)

Calculation of intrinsic carrier concentration in Hg1−xCdxTe

Abstract: Intrinsic carrier concentration in Hg1−xCdxTe is calculated as a function of temperature and composition using the Kane nonparabolic approximation for band structure and recent measurements of the heavy hole mass mh and energy gap Eg. An expression fitted to these calculations is: ni[5.585−3.820x+1.753(10−3)T −1.364(10−3)xT] ×(1014)E3/4gT3/2 exp(−Eg/2kbT). The fit of this approximation is within 1% of the calculated ni for the range Eg>0, 50

The exponential optical absorption band tail of Hg1−xCdxTe

Abstract: The optical absorption edges of Hg0.71Cd0.29Te and CdTe were measured over the temperature range 80≤T≤300 K. The refractive indices of these materials are determined over a large energy range at T=300 K and their dispersion relation is given. The absorption band tail of Hg1−xCdxTe has an exponential shape. Its slope increases with decreasing temperature. It is suggested that this tail is not caused by permanent lattice disorder but is a material property. An empirical expression for the absorption coefficient as a function of temperature and composition is derived. Using this expression, the zero‐intercept cut‐on energy of the infrared transmission spectrum at room temperature is used to define the composition for any desired thickness of Hg1−xCdxTe sample.

Teledyne Imaging Sensors: infrared imaging technologies for astronomy and civil space

Abstract: Teledyne Imaging Sensors develops and produces high performance infrared sensors, electronics and packaging for astronomy and civil space. These IR sensors are hybrid CMOS arrays, with HgCdTe used for light detection and a silicon integrated circuit for signal readout. Teledyne manufactures IR sensors in a variety of sizes and formats. Currently, the most advanced sensors are based on the Hawaii-2RG (H2RG), 2K×2K array with 18 μm pixel pitch. The HgCdTe detector achieves very low dark current (<0.01 e-/pixel/sec) and high quantum efficiency (80-90%) over a wide bandpass. Substrate-removed HgCdTe can simultaneously detect visible and infrared light, enabling spectrographs to use a single focal plane array (FPA) for Visible-IR sensitivity. The SIDECARTM ASIC provides focal plane electronics on a chip, operating in cryogenic environments with very low power (<11 mW). The H2RG and SIDECARTM have been qualified to NASA Technology Readiness Level 6 (TRL-6). Teledyne continues to advance the state-of-the-art and is producing a high speed, low noise array designed for IR wavefront sensing. Teledyne is also developing a 4K×4K, 15 µm pixel infrared array that will be a cost effective module for the large focal planes of the Extremely Large Telescopes and future generation space astronomy missions.