GaAs-Based Infrared Photodetection And Photon Up-Conversion Devices

Due to its excellent electronic and optical characteristics as well as mature fabrication technology, GaAs material has been widely employed in photoelectronic devices in the infrared region.By the aid of a set of GaAs/AlGaAs quantum-well photodetectors (QWIPs) with otherwise identical device parameters but the doping density, we have systematically studied the influence of doping density on the photodetector perfermance. The experimental results conincide well with the standard theory of QWIPs, suggesting the validity of the theory. We have also experimentally verificated the theoretically predicted optimal conditions for optimized background limited perfermance temperature Tblip (Ef =kBTblip) and detector noise limited detectivity Dd *et (Ef =2kBT). Based on above results, we have furthered the discussion and given the guidelines to reach optimal QWIP performance. We suggest the optimal doping density of QWIPs should be determined according to application and the desired operating temperature.In addition to GaAs-based QWIPs, we have further studied GaAs-based p-i-n photodetectors employing the direct band gap of GaAs. In order to work in the infrared region beyond 1μm, In or As is added to the GaAs material to reduce the band gap. However, the lattice mismatch between the GaAs substrate and InGaAs detector active layer increases rapidly with In or As content, making it difficult to grow photodetectors lattice matched to GaAs working in the eye-safe region through direct epitaxial growth. Fortunately, it has been found that the incorporation of a small amount of nitrogen into InGaAs or GaAsSb material can reduce the band gap as well as lattice constant. We have successfully fabricated GaNAsSb/GaAs p-i-n photodetectors with effective detection ranges between 0.75 and 1.50μm. XRD rocking curve measurement indicates a very small lattice mismatch between the GaNAsSb layer and GaAs substrate.An alternative method for infrared detection and imaging is the up-conversion method, i.e., to convert infrared light to shorter wavelength that can be detected by Si charge-coupling devices (CCD). The next significant progress of the NIR up-conversion technology is to realize a full GaAs-based approach by taking advantage of the mature GaAs material to grow both the photodetector and LED on GaAs substrate via epitaxial growth integration. In this letter, we report on the demonstration of room-temperature full GaAs-based NIR up-conversion by connecting the GaNAsSb/GaAs photodetector in series with a commercial GaAs/AlGaAs LED. Due to the avalanche gain in GaNAsSb/GaAs photodetectors resulted from mid-gap As antisite defects and high internal efficiency in GaAs/AlGaAs LEDs, the up-conversion efficiency of the integrated system reaches 0.048 W/W under -7 V bias, much higher than any existing NIR upconverters without amplifying structures. The present work establishes an experimental base for direct epitaxial growth of full GaAs-based NIR upconverters with high up-conversion efficiencies.