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Self-assembled InAs quantum dots (QDs) over an InGaAs layer on InP substrates were grown by metalorganic chemical vapor deposition. Their structural and optical properties were investigated by atomic force microscopy and photoluminescence. Optimised stacks of structures were grown for a QD infrared photodetector and their absorption was measured. Magnetotransport measurements on the stacked QD structures revealed tunneling between quantum dot states with an applied magnetic field parallel to the current. 1 Introduction Infrared photodetectors based on intersubband transitions have received a great deal of attention for applications such as image recognition, atmospheric communications and toxic gas detection. In quantum well infrared photodetectors (QWIPs) the selection rules of the intersubband transitions prevent normal incident light from being absorbed [1]. To overcome this limitation, complex fabrication steps such as grating coupling is required [2]. On the other hand, quantum dot (QD) infrared photodetectors (QDIP) offer the prospect of normal incidence intersubband detection [3] due to the QD three dimensional character. Furthermore, QDIPs can have a broader infrared response range [4] and a higher responsivity due to the longer lifetime of excited electrons [5], which could also be exploited to increase the operating temperatures of these devices. However, for the QDIPs to replace the QWIPs a high density of dots is needed, as well as an uniform QD distribution. Multicolor [6,7] and high detectivity [5] QDIPs have been achieved recently for the mid-and the far-infrared ranges.Stacked self-assembled doped QDs form the QDIP structure. In particular, the so-called dot-in-a-well (DWELL) structure [8] is promising for QDIPs because the presence of a QW allows the bound-tobound transition from the ground state of the dot to a state in the well to be tuned by changing the QW thickness without modifying the QD structure.In recent years, there have been many studies of magnetotransport in self-assembled QDs, including magnetotunneling measurements to probe the electronic states of the quantum dots [9] and investigations of tunneling through double layers of stacked InAs dots [10]. However, so far there have been very few investigations on magnetotransport in stacked multi-layers of QDs, especially of magnetotunneling with the magnetic field applied parallel to the tunneling current.

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