Normal-incidence far-infrared detectivity of InAs/GaAs QDIPs doped in dots and barriers

We report some comparative results on the normal-incidence device characteristics accomplished with a couple of self-assembled InAs/GaAs quantum-dot infrared photodetectors (QDIPs) doped in InAs QDs and GaAs barriers. The peak values of responsivity and detectivity for the barrier-doped device are 650 mA/W and 3.2 x 10(8) cm Hz(1/2)/W (18 K) at lambda(p) congruent to 5 mu m, respectively, which are approximately two and ten times higher than those for the QD-doped one. In addition, while there is no spectral response over 6 pm in the QD-doped structure, a strong photoresponse is extended up to around 10 pm in the barrier-doped one. Although the direct doping in InAs QDs is effective for blocking the dark current, the doping in GaAs barriers has better device performance of QDIP. (c) 2005 Elsevier B.V. All rights reserved.