Blue light‐emitting diodes grown by plasma‐assisted molecular beam epitaxy

Blue light emitting diodes (LEDs) were grown by rf-plasma assisted molecular beam epitaxy on GaN templates having threading dislocation densities of ∼8 × 107 and ∼1 × 109 cm−2. The dependence of light-current curves on device size indicated the existence of non-radiative leakage paths and electron overflow from the active region into the p-doped cap layer. Current-voltage measurements revealed significant reverse-bias leakage and forward series resistance. Packaged devices grown on the ∼1 × 109 cm−2 template show maximum output powers of 0.28 mW at 20 mA forward current. An increase in output power was observed during 1000 h lifetime tests. These findings support the hypothesis that a large number of leakage paths exist in these devices. LEDs grown on the template with a lower dislocation density showed a decrease in leakage current and an increase in output power. Thus, the main leakage path is supposed to be related to threading dislocations. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)