Improvement of Quantum Efficiency in Gallium Arsenide Electroluminescent Diodes

The external quantum efficiency of Sn, Se or Te doped GaAs electroluminescent diodes in the 1×10 16 to 1.5×10 18 /cm 3 carrier concentration range was investigated. A maximum luminescence efficiency can be obtained in the 5∼7× 17 /cm 3 range at 300° and 77°K. The effect of carrier concentration on the external quantum efficiency was considered on the basis of a simple assumption. The existence of the maximum efficiency in the 5∼7×10 17 /cm 3 range was clarified from the fact that the external quantum efficiency was determined by the injection ratio of electrons and the bulk absorption for the photons, provided the fraction of electrons injected into the p -type side of the junction which recombined radiatively was not affected by the doping level in the n -type side. The doping effect on the external quantum efficiency was evidently seen for Sn doped diode. The electroluminescent GaAs diodes of the p + - n + - n structure in order to improve the injection ratio and to reduce the bulk absorption. The external quantum efficiency of the p + - n + - n structure fabricated with the liquid-phase epitaxy was improved by a factor of 10∼20 in comparison with the usual structure.