Light emitting diodes from MOVPE-grown p- and n-doped II-VI compounds

A critical review is given of the present state, the problems and the prospects of MOVPE-growth of II-VI LEDs. It is shown that MOVPE-growth on (001)GaAs substrates occurs preferentially in a three-dimensional growth mode independent of substrate preparation. ZnSxSe1-x grows in good quality over the whole range of composition x. Good quality of ZnxCd1-xSe was only obtained for low Cd-concentrations. Improvements can be expected from the use of new precursors. The n-doping of ZnSe and ZnSxSe1-x presents no problem when n-butylchloride is used. Carrier concentrations can be as high as n greater than or equal to 10(18). Various nitrogen compounds have been used to achieve p-doping of ZnSe by MOVPE. We show that quite large concentrations of nitrogen can be incorporated by photoassisted MOVPE with phenylhydrazine as precursor. The nitrogen doped samples are usually highly compensated independent from the special doping procedure. Proper annealing can activate at least part of the incorporated nitrogen. The preparation of appropriate diode structures presents no special problems, however their room temperature (RT) luminescence efficiency is still low but may be considerably improved with increasing purity of precursors.