Double Injection in GaP Electroluminescent Diodes

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Abstract
Electrical and optical properties accompanied with double injection and negative resistance in GaP electroluminescent diodes were investigated at 77°K. A region, where current is proportional to the square of the applied voltage and marked changes occurs in luminescence spectra, was observed. By pulse measurements, switching time to the negative resistance was found to be an order of msec. The double injection is caused by hole injection into the high resistivity n-region. A new theory of double injection is formulated, taking into account charge neutrality and boundary condition of carrier injection. The square-law is associated with densities of recombination centers larger than the injected carrier density. This theory explains the experimental results satisfactorily. Immediate cause of the negative resistance is considered to be a rise of sample temperature.