Ge quantum dots on silicon for terahertz detection
Terahertz has attracted attention from both millimeter and infrared technologies. Currently, solutions consist of expensive sensor systems limiting the amount of applications. To obtain a low cost solution, one approach is to use thermistor material based on Ge on Si quantum dots on microbolometers. It has been demonstrated that SiGe monocrystalline materials have superior properties to amorphous silicon or VOx regarding the temperature coefficient of resistivity and 1/f noise. Unfortunately, the calculated critical thickness for strained SiGe material show unreasonable layer thickness for high Ge amounts. To avoid this, Ge dots instead of SiGe layers are preferred. This article focuses on optimizing the thermistor properties of Ge-dots. All samples were grown on Si (100) substrates in a temperature range of 500-650 C at 20 torr by RPCVD. They were characterized (XRD, HRSEM and AFM etc.) determining the diameter, thickness, density and uniformity. Fourier transform photoluminescence was performed to find the spatially direct (EA) and indirect (EB) bandgap transitions.
Group IV Materials for Low Cost and High Performance Bolometers
Infrared (IR) imaging has absorbed a large attention during the last two decades due to its application in both civil and military applications (Per Ericsson et al., 2010; Lapadatu et al., 2010; Sood et al., 2010). Thermal detector is presently revolutionizing the IR technology field and it is expected to expand the market for cameras. These detectors are micro-bolometers and are manufactured through micro-maching of a thermistor material. Since these detectors demand no cryogenic cooling, they provide the opportunity for producing compact, light-weight, and potentially low-cost cameras. The preferred functioning wavelength regions for these detectors are usually 8–12 ┤m due to the high transparency of the atmosphere in these regions.
FOA/DSTO uncooled IRFPA development
This paper aims to update the progress of the FOA and DSTO collaboration on uncooled microbolometer focal plane arrays and digital readout CMOS electronics, and reports on problems and solutions found in the electronics area. Image result are presented showing the feasibility of the FOA/DSTO concept. This concept utilizes monolithic silicon microbolometers and unique 16-bit on-chip analog-to-digital conversion. The focal plane arrays described in the paper were designed by Electro-optic Sensor Design and post- processed at DSTO on to CMOS readout wafers supplied by FOA. All electronics including the 16-bit ADCs have been proven to function up to the sensors format 320 X 240, using 320 parallel channels of electronics. No significant performance degradation has been observed compared to smaller 16 X 16 arrays. Given detector performance obtainable today and low noise preamplification, the dynamic range supplied by this ADC is sufficient to give an NETD better than 0.1K using 40 micrometers X 40 micrometers pixels and f/1 optics while covering a +/- 5 percent detector mismatch. This is sufficient for most applications but analog offset correction prior to A/D conversion will be necessary to achieve a readout noise lower than the detector Johnson noise.