Korean Journal of Materials Research ISSN:1225-0562(Print) 2287-7258(Online) 한국재료학회지

We investigate the characteristics of self-assembled quantum dot infrared photodetectors(QDIPs) based on doping level. Two kinds of QDIP samples are prepared using molecular beam epitaxy : n⁺-i(QD)-n⁺ QDIP with undoped quantum dot(QD) active region and n⁺-n⁻(QD)-n⁺ QDIP containing Si direct doped QDs. InAs QDIPs were grown on semi-insulating GaAs (100) wafers by molecular-beam epitaxy. Both top and bottom contact GaAs layer are Si doped at 2×10¹⁸/cm³. The QD layers are grown by two-monolayer of InAs deposition and capped by InGaAs layer. For the n⁺-n⁻(QD)-n⁺ structure, Si dopant is directly doped in InAs QD at 2×10¹⁷/cm³. Undoped and doped QDIPs show a photoresponse peak at about 8.3 μm, ranging from 6~10 μm at 10 K. The intensity of the doped QDIP photoresponse is higher than that of the undoped QDIP on same temperature. Undoped QDIP yields a photoresponse of up to 50 K, whereas doped QDIP has a response of up to 30 K only. This result suggests that the doping level of QDs should be appropriately determined by compromising between photoresponsivity and operating temperature.