InGaAs-Avalanche-Photodioden für bildgebende Verfahren im kurzwelligen Infrarot

High-sensitivity InGaAs-detectors for the short-wave infrared (SWIR) reveal a number of interesting properties which can be beneficially used in industrial process control or in defense and security applications. Manufactured as a high-resolution detector-array for an imaging technique, night-vision devices can be built to detect the natural night-glow radiation. Using infrared LEDs or lasers around 1.55 ?m wavelength, enclosed areas or remote objects can be illuminated or targeted. Furthermore, an exact distance information can be calculated from the time-of-flight of a pulsed laser signal using high-bandwidth and high-sensitivity detectors. Compared to visible light, short-wave infrared radiation enables a significantly improved vision through fog or smoke. Thanks to the relatively large bandgap of InGaAs, the devices can be operated with moderate or even without any cooling. Since for all these applications a very low photon flux has to be expected, avalanche-photodiodes (APDs) with an internal signal amplification are beneficial. The aim of this work was to build a high-resolution detector-array based on InGa- As/InAlAs-APDs for a high-sensitivity SWIR-camera. This way the internal signal amplification of the APDs can be utilized on camera-chip level. Here, the most challenging task was to realize an operating-voltage of the APDs below 20V bias and simultaneously a very low dark current. Due to consequent optimization of InGaAs/InAlAs-APD-structures, the first high resolution InGaAs/InAlAs-APD-array with 640 × 512 pixels could be demonstrated within this work. Implemented in a camera-setup, a gain of up to 8.5 on camera chip level could be achieved. The high operating-temperature of up to 260K can basically be realized with moderate cooling using thermoelectric devices. Bandedge and Monte-Carlo-simulations as well as electro-optical characterization of a variety of APDs enabled a significant optimization of the grading- and charge-layers of the APD structure. The optimized APDs reveal a gain of 10 at 18.5V whereas the dark-current density is as low as 2.5•10 -4 A/cm(2). This represents the lowest operating-voltage with a simultaneous low dark current, which has been published for the InGaAs/InAlAs and the InGaAs/InP-material system so far