Extrinsic doping in MOVPE of HgCdTe has been a critical issue for the successful growth of high performance detector devices. In this paper recent progress achieved in this area are reviewed. New results are reported on the strong dependence of iodine doping on the crystal orientation of HgCdTe. It is shown that the iodine incorporation efficiency from ethyl iodide varies by as much as three orders of magnitude depending on the misorientation of the substrate from the (100) plane towards (111)A/B. To demonstrate progress in MOVPE in situ growth of HgCdTe p-on-n heterojunction detectors, detailed characterization results for photodiodes with cutoff wavelengths of 12.7 μm at 80 K are reported.