Mid-Wave and Long-Wave Single Uni-polar Barrier Infrared Detectors Based on Antimonide Material Systems

Infrared detectors are very important technological tools for many different applications. Infrared detectors have existed as far back as the late 1700s but received a tremendous push 200 years later during World War II. Both thermal and photon based infrared detectors have had significant advancements with many different varieties becoming available with varying degrees of sensitivity, speed, and wavelength sensitivity. One of the best performing technologies is based on Mercury Cadmium Telluride. However, it still has limitations with regard to low operating temperature, material yield and processing difficulties. A newer material technology known as type-II indium arsenide/gallium antimonide strain-layered superlattice has received much attention for its potential superior performance from lower dark current, mature III-V material fabrication techniques, and design versatility. However, superior dark current performance has yet to be realized due to large Shockley-Read-Hall generation-recombination current. To overcome this, researchers have taken advantage of the versatile bandstructure of the superlattice material and have created heterostructure designs to reduce dark current. These designs include the nBn, CBIRD, pMp, and pBiBn. These designs have enabled detectors have dark current behavior to be within a factor of 2 of HgCdTe based detectors. The more basic of these designs, the nBn, has been utilized in InAs detectors, InAsSb detectors, HgCdTe detectors, and both mid and long-wave superlattice detectors with success. However, questions and optimization remain regarding dark current and photocurrent behavior, band alignment, and photoconductive gain. Mid-wave InAsSb nBn detector designs with different barrier composition and doping conditions have been investigated to help elucidate effects on dark current and photoresponse. Mid-wave superlattice nBn detectors with different absorber doping conditions have been studied as well. Dark current was found to be decreased by lightly doping the barrier layer n-type. variations of the nBn design, such as the pBn and pBp have been implemented with long-wave superlattice detectors and their bias and temperature dependent dark current and photoresponse have been studied. Also, the photoconductive gain of a long-wave pBp detector have been measured and found to be slightly less than unity.