Implantation of rare-earth ion into ZnSe and ZnS crystals has been used to fabricate light emitting diodes

[1-4]

. ZnS:Er

Nd MS diodes also have been fabricated which give different colours of electroluminescence emission when the efxcitation parameters are changed

[9]

. In this report

the variable colour ZnSe:Er

3+

MIS diodes are depicted which are made by means of effective luminescent centers under high

[5

8]

and low

[7

8]

electric field excitation

as shown in Fig.1.ZnSe crystals were grown by sublimation method. The dice with demen-sions of 6×6×1 mm

3

were annealed in the molten zinc to reduce their resistivities to the range of l-10Ω·cm. Erbium ions with energy of 100keV and dose of 1×10

15

cm

-2

were implanted into ZnSe substrate at room temperature. Annealing was performed in the molten zinc to eliminate the radiation damage

[11]

. After annealing

an In ohmic contact was made on the substrate. A thick layer (-600Å) of ZnSe was deposited on the implantation surface by evaporation and finally a circular gold electrode (1 mm in diameter) was evaporated on the top of ZnSe layer.Fig.2 shows electroluminescence spectra of the variable colour ZnSe:Er

3+

MIS diodes. It is easily found that the diodes give green electroluminescence of Er

3+

when reverse biased

and give near band edge emission in blue when forward biased. The luminescent colour is changed with the polarity of applied voltage in this kind of diodes.The luminescent mechanism of the diodes is the high field direct impact excitation when they are reverse biased

[2-4]

. And the blue near band edge luminescence under forward bias could be explained by the hot holes injection

[10]

as shown in Fig.1.