SPECTRA OF SUPERBRIGHT BLUE AND GREEN INGAN ALGAN/GAN LIGHT-EMITTING-DIODES/

Electroluminescence spectra of blue and green light-emitting diodes (L EDs) based on InxGa1-xN/ AlyGa1-yN/GaN heterostructures with a thin qu antum well active layers were studied at currents J = 0.01-20 mA. Spec tral maxima of blue LEDs are (h) over bar omega(max) = 2.58-2.75 eV, o f green are (h) over bar omega(max) = 2.3-2.45 eV, depending on the In content in the active layer. The low and high energy tails of the spe ctra are exponential with the parameters E-0 = 42-50 meV and E-1 appro ximate to 1-1.3 kT, respectively. The spectra can be described taking into account quantum-size effects, impurities and fluctuations in acti ve layers. An interference structure in spectra was detected. Light in tensity depended on J linearly in the interval 1-20 mA. Efficiency of blue LEDs dropped at J <0.7 mA as I similar to J(4-5) (300 K). The gre en LEDs had no such dependence. Tunnel radiation spectra with maxima m oving with the voltage were detected at low J. (C) 1997 Elsevier Scien ce Limited.