| Popis: |
Efficient electroluminescence in GaP diodes has been obtained both in the red and green portions of the spectrum. The former results from recombination at Zn-O centers and the latter from recombination at N centers. Since these centers can be introduced independently, varying hues between red and greeen can be obtained by varying the relative intensities of the emitted red and green radiation. This can readily be done at a normal operating current density of ≈ 10 A/cm 2 by varying doping concentrations. However, it is also possible to change the hue with a fixed impurity distribution by varying the diode current. This electrical variability stems from the fact that the red centers saturate at a current density of about 5 A/cm 2 but the green centers do not. Thus at low forward current, the red luminescence can dominate the green, while at high current, the reverse holds. An analysis is presented giving the dominant wavelength and luminous efficiency as a function of green to red intensity ratio. The achievable hue variation and luminous efficiency is illustrated for two different, nonoptimized, red-green diodes. |
