MOVPE GROWTH AND CHARACTERIZATION OF DOPED CDXHG1-XTE STRUCTURES

This paper describes work carried out towards achieving extrinsically doped CdxHg1-xTe (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 approximately 400-degrees-C with diethyltellurium (DET) as the tellurium alkyl source. The two dopants used were arsenic, introduced as AsH3, and iodine, as vapour from the solid element. The donor doping range has been extended by the 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. Depth profiling to obtain the electrical characteristics, chemical dopant 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 approximately 1 x 10(17) I (atomic) cm-3 n-type regions on (1-4) x 10(16) atoms As cm-3 p-type regions have also been obtained which show sharp electrical junctions.