Dark Current Reduction in Near Infrared P-I-N Detector Diodes Fabricated from In.75Ga.25As Grown by Molecular Beam Epitaxy on InP Substrates

ABSTRACTWe have investigated several approaches to improve the material quality of lattice-mismatched In.75Ga.25As grown by Molecular Beam Epitaxy (MBE) on (100) InP substrates. They include linear grading of In composition from lattice matched In.53Ga.47As to In.75Ga.25As in a 1 μm buffer layer grown at reduced substrate temperature, in combination with various in situ annealing and material regrowth steps. The material was used for fabrication of mesa-structure p-i-n photodetectors with 2.2 μm cutoff wavelength. The room temperature dark current density at 1 V reverse bias was approximately 2 mA/cm2 in all structures that were subjected to anneal and regrowth process, a factor of three improvement over reference samples which were not subjected to annealing and regrowth. The dark current density at 15 V reverse bias (10 mA/cm2 for the best devices) was at least two orders of magnitude lower in all annealed samples than in reference samples. These results suggest that the MBE grown material can be an attractive alternative to the vapor phase epitaxy (VPE) grown material which is commonly used for fabrication of these detectors.