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In two recent review papers on metal organic vapour phase epitaxy (MOVPE) of cadmium mercury telluride (CMT) particular emphasis was placed on the crucial importance of doping studies to the realization of future device structures. If the full potential of MOVPE growth of CMT is to be realized then extrinsic doping of heterostructures is required. If the doping and composition junctions can be grown wiin tine correci degree of grading then inis wili creaie ihe poteniiai ior ?ne production of device structures leading to either improved performance and/or increased operating temperatures. This paper will review published doping studies and also present some recent results on both acceptor and donor doping studies carried out by the authors. In the latter studies, interdiffused multilayer process (IMP) growth of CMT has been performed at 0360 "C using dimethyl cadmium (DMC) and di-isopropyl tellurium (DIPT) as the MO precursors while t h e Hg overpressure was provided by a heated elemental source. Alternative acceptor doping sources to arsine have been investigated including phosphine, triphenyl arsenic, and phenyl arsenic of which the latter appears to be most suitable. Iodine has continued to show the donor dopant potential in CMT that it exhibited with higher-temperature (0400 "C) MOVPE growth using di-ethyl tellurium (ET). Characterization o i iuiiy doped structures wiii be described.

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This paper describes work carried o u t towards achieving extrinsically doped Cd,Hg, -,Te (CMT) heterostructures grown with stable dopants and sharp junctions. Both acceptor and donor doping of CMT has been achieved in our MOVPE growth reactor using the interdiffused multilayer process at -400 "C with diethyitellurium (DET) as the tellurium alkyl source. The two dopants used were arsenic, introduced as ASH,, and iodine, as vapour from the solid element. The donor doping range has been extended by t h e use of a concentrically arranged double-injection-tube system which reduced the pre-reaction between the cadmium alkyl and the iodine vapour. investigations have been carried out into the growth of various double-layer structures which incorporate either a single dopant transition or a double transition, as in a fully doped structure. concentrations and alloy compositions of As-doped ( x = 0.3) on undoped (x = 0.21) CMT heterostructures has shown that pn structures have been produced after suitable Hg anneal treatments. Iodine-doped x = 0.2 layers on As-doped x = 0.3 layers have also exhibited pn transitions. Results from fully doped homojunction layers grown with -1 x IO" I (atomic) cm --3 n-type regions on ( 1 4 ) x IO" atoms Ascm-" p-type regions have also been obtained which show sharp electrical junctions.Depth profiling to obtain the electrical characteristics, chemical dopant