INFLUENCE OF DEFECTS ON THE ELECTRICAL AND OPTICAL CHARACTERISTICS OFBLUE-LIGHT-EMITTING DIODES BASED ON III-V NITRIDES

We have measured the electrical and optical properties of blue light-e mitting diodes (LEDs) based on III-V nitrides. The current-voltage cha racteristic is described by means of the relation I = I-0 exp(alpha V) . In this equation alpha is temperature independent, suggesting a proc ess of conduction by tunneling, as was recently reported also for blue -green LEDs based on III-V nitrides [Appl. Phys. Lett. 68, 2867 (1996) ]. We explain the differences between blue and blue-green devices taki ng into account the tunneling process across semiconductor interfaces, in which a great number of defects is present. The light output inten sity of the LED as a function of junction-voltage data reveals a depen dence on the junction-voltage of the type L = L(0) exp(qV/1.4 KT), ind icating that the radiative recombination path is via deep levels locat ed at the forbidden gap. Furthermore, we find that the light output-cu rrent characteristic follows a power law like L proportional to I-p. F rom the analysis of data it appears that, contrary to expectations, th e nonradiative centers are saturated at very low current values that a re comparable to the values at which this saturation takes place in LE Ds based on III-V arsenides with a low content of defects. (C) 1997 Am erican Institute of Physics.