Effect of indirect minima carrier population on the output characteristicsof AlGaInP light-emitting diodes

We show that carrier transfer to the indirect X level in the confining laye r is responsible for most of the substantial decrease in the efficiency of AlGaInP light-emitting diodes (LEDs) operating at short wavelengths. Carrie r transfer to the confining X level was obtained by reducing the separation between the AlGaInP direct Gamma minimum and the X levels by varying the A l composition in the active region and by the application of hydrostatic pr essure. Carrier transfer to the confining X level appeared as an additional peak in the electroluminescence (EL) and resulted in a significant decreas e of the LED efficiency. A simple model of the EL emission that takes into account carrier population in the X minima was found to be in excellent agr eement with the measured EL behavior. (C) 1999 American Institute of Physic s. [S0003-6951(99)04946-3].